4_i__-_Crystal_Reservoir_Rehabilitation_Plan_and_Construction_Sequence.pdf

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Crystal Reservoir Rehabilitation Plan:

Table of Contents

1 Introduction

1.1 Project Location

1.2 Background

1.3 Management Species of Concern

1.4 Ecological Impacts of Dam Removal

2 Restoration Design

2.1 Hydrology of the Crystal Reservoir Drainage Basin

2.2 Crystal Reservoir Dam: Specifics

2.3 Project Design Overview

2.3.1 Sediment Management and Toxicity Testing

2.3.2 Lowering the Dam Embankment

2.3.3 The Spillway

2.3.4 Outlet pipe

2.3.5 Restored Crystal Reservoir Drainage Channel

2.4 Permits

3 Crystal Reservoir Construction Sequence

3.1 Construction Timing

3.2 Pre-Construction

3.2.1 Pre-Job Conference

3.2.2 Collect and Move Native Aquatic Organisms and Rare Plants

3.2.3 Construction Staking

3.2.4 Mobilization and Construction Access

3.3 Construction

3.3.1 Dewater Project Site

3.3.2 Removal of Outlet Siphon Pipes

3.3.3 Removal of Crystal Dam

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3.3.4 Restore Natural Drainage Channel through Former Reservoir Basin

3.3.5 Finished-Grading and Soil Decompaction

3.4 Post-Construction

3.4.1 Site Cleanup

3.4.2 Revegetation

4 Recommended Equipment

5 Measures Taken to Minimize Impact

5.1 Protection of Vegetation and Sensitive Species

5.2 Protection of Cultural Resources

5.3 Water Quality Control

5.4 Air Quality Control

6 Best Management Practices (BMPs)

7 References

8 Appendix A: AutoCAD Design Plans

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Crystal Reservoir Rehabilitation Plan

1 INTRODUCTION

Crystal Reservoir, a man-made impoundment located within Ash Meadows National Wildlife Refuge, creates deep-water habitat that supports populations of non-native sport fish, results in altered hydrology downstream from the dam and has a risk of catastrophic failure during flood events or as earthen embankments deteriorate over time with lack of proper maintenance. Reasons for the removal of dams at Ash Meadows include, but are not limited to: restoration of natural hydrology, protection of endangered plants, wildlife, and their habitat, removal of non-native species, and protection of human life and infrastructure downstream from the high hazard structure. In addition, removal of the dam will help restore geomorphic dynamics and ecological function, thereby returning a large portion of the Crystal Slough to a natural condition. Otis Bay, Inc. developed the following document and set of plans for the removal of the Crystal Reservoir Dam.

1.1 Project Location

Ash Meadows National Wildlife Refuge is located in Amargosa Valley in southern Nevada.

Crystal Reservoir is located near the center of the refuge, approximately 0.5 miles directly south of refuge headquarters and 0.65 miles from Spring Meadows Road, off of Crystal Loop Road.

Figure 1-1. Crystal Reservoir location map.

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1.2 Background

Crystal Reservoir, an in-channel impoundment, is located within the Crystal Management Unit (CMU) of Ash Meadows National Wildlife Refuge (AHME). The CMU includes the drainages of Crystal, Point of Rocks, Kings, Forest, Tubbs, and Bradford Springs. Prior to the arrival of settlers at Ash Meadows, outflow from Point of Rocks, Kings Spring, and Forest Spring flowed southwest through separate drainages toward the location of present-day Ash Meadows Road, and Tubbs and Bradford Springs discharged west toward present-day Lower Crystal Reservoir.

Water from Crystal Spring discharged to the west, where it was dammed by an extensive line of wind-blown sand dunes and once formed a large wetland alongside the line of dunes. During the period of agricultural modifications at Ash Meadows, outflow from springs of the Crystal Management Unit was collected in irrigation ditches, many of which remain in place today (Otis Bay, Inc and Stevens Ecological Consulting, LLC 2006). Crystal Reservoir Dam was constructed in 1971 (Lindon 2009) for irrigation water storage, impounding water diverted from Crystal Spring in a large reservoir. Non-native species such as green sunfish and largemouth bass were released into the reservoir for sport-fishing, and populations remain there today. Presently, water from Crystal Spring discharges into a portion of restored channel then into irrigation ditches, with outflow divided between Crystal Reservoir and Horseshoe and Lower Crystal Reservoirs. Man-made berms impound water in Horseshoe and Lower Crystal Reservoirs, resulting in deeper and colder-than-natural aquatic habitat in the area below the dam (Otis Bay, Inc and Stevens Ecological Consulting, LLC 2006); (Threloff 1992).

Ash Meadows became a National Wildlife Refuge in 1984, ending the period of ranching, agriculture and land development at this site. Today, Crystal Reservoir is no longer needed for storage of irrigation water, and the risk of dam failure increases over time as earthen embankments deteriorate and water seeps through the foundation. Leaving the Crystal Reservoir Dam in place would require repairs and improvements to bring the dam up to current Nevada and FWS safety standards, such as seepage and internal erosion control measures, seismic stability, spillway repair and erosion control, vegetation removal, outlet repairs or replacement, re-grading crest and slopes for slope stability, and riprap reinforcement (Lindon 2009). Additionally, Crystal Reservoir provides habitat for non-native species such as green sunfish and largemouth bass, which prey on and compete for resources with Ash Meadows native endemic fish species (US Fish and Wildlife Service 2009).

In 2009, the FWS produced a Comprehensive Conservation Plan (CCP) for Ash Meadows National Wildlife Refuge, outlining restoration goals and future management actions.

Alternative C, the Refuge’s preferred alternative, calls for the modification or removal of Crystal Reservoir to minimize adverse environmental effects on special-status species and to alleviate potential concerns for visitor safety and refuge management (US Fish and Wildlife Service 2009). It was noted in the CCP that public use of Crystal Reservoir for swimming and fishing was not compatible with human safety, refuge purposes, biological integrity, diversity, or the environmental health of the refuge.

Goals expressed in the 2009 CCP for the removal of Crystal Reservoir Dam include:

Reduction of open water habitat and restoration of native stream channels, to reestablish historic hydrology and allow for native habitat restoration.

Reduction of potential for flooding downstream of the reservoir, an action beneficial to human safety and the natural environment.

Reduction or elimination of populations of non-native predatory fish that reside in Crystal Reservoir.

1.3 Management Species of Concern

Very few of Ash Meadows’ native endemic aquatic species are known to use Crystal Reservoir, as most prefer shallower marsh, stream, or spring pool habitat. Ash Meadows Amargosa pupfish are present in Horseshoe and Lower Crystal Reservoirs in low numbers when bass and green sunfish are present. Pupfish populations in the reservoirs tend to increase following invasive species treatments, and decrease when non-native species return (C. Baldino, personal communication 2012). Pupfish are numerous in the shallow marshy stream between Crystal Reservoir and Lower Crystal Reservoir. Odonata (dragonfly and damselfly) diversity was higher in the Crystal Reservoir and Lower Crystal Reservoir areas than anywhere else on refuge (Otis Bay, Inc and Stevens Ecological Consulting, LLC 2006). Crystal Reservoir is also used by native waterbirds. Waterfowl hunting is allowed on the southern portion of Crystal Reservoir and in Lower Crystal Reservoir.

Crystal Reservoir provides deep-water habitat for several non-native species of fish, which act as predators and compete for resources with native fish populations upstream (US Fish and Wildlife Service 2009). Recent surveys in 2010 and 2011 by Scoppettone, et. al. (2012) captured green sunfish and largemouth bass in Crystal Reservoir. Green sunfish were found below the dam in Lower Crystal Reservoir, and both species were captured in Horseshoe Reservoir as well (Scoppettone, et al. 2012). In the past, Crystal Reservoir has provided habitat for invasive species such as mosquitofish, sailfin molly, largemouth bass, black bass, green sunfish, and bullfrogs (Otis Bay, Inc and Stevens Ecological Consulting, LLC 2006). Fishing is not allowed at AHME. Table 1-1 lists native and introduced aquatic species and their distribution in the Crystal Springs drainage.

The largest population of Amargosa niterwort (Nitrophila mohavensis) within AHME grows below Crystal Reservoir on salt-encrusted alkaline flats. It is a federally listed endangered species and a member of the goosefoot family (Chenopodiaceae)(Otis Bay, Inc and Stevens Ecological Consulting, LLC 2006). Ash Meadows blazingstar (Mentzelia leucophylla) is found in drainages about 0.2 miles above Crystal Reservoir (Bio-West, Inc. 2011). Table 1-2 lists plant species of conservation concern found in the vicinity of Crystal Reservoir.

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Table 1-1. Management species of concern in Crystal Spring Pool (CSP), Crystal Channel (CC), Crystal Reservoir (CR), Horseshoe Reservoir (HR), and Lower Crystal Reservoir (LCR).

Species Species Information Current Distribution

Ash Meadows Amargosa pupfish Cyprinodon nevadensis mionectes

Native, endemic, Endangered

Present in CSP, CC, HR and LCR (2012).

Crystal Spring springsnail Pyrgulopsis crystalis

Native, endemic, Candidate for Federal listing

Present in CSP (1987).

Sportingoods tryonia springsnail Tryonia angulata

Native, endemic, Candidate for Federal Listing

Present in CSP (1987).

Crayfish Procambarus clarkia

Introduced Present in HR (2012).

Mosquitofish Gambusia affinis

Introduced Present in HR and LCR (2012).

Sailfin Molly Poecelia latipinna

Introduced Present in HR (2012).

Largemouth Bass Micropterus salmoides

Introduced Present in CR and HR (2012)

Green Sunfish Lepomis cyanellus

Introduced Present in CR, HR and LCR (2012)

Sources: Otis Bay, Inc and Stevens Ecological Consulting, LLC 2006; Scoppettone, et al. 2012; Bio-West 2011;

Hershler and Sada 1987.

Table 1-2. Rare plant species of Conservation Concern in Crystal Spring, Reservoir, Lower Crystal Reservoir, and Horseshoe Marsh, outflow channels, and vicinity (Table modified from Bio-West 2011).

Species Agency Status Nevada Heritage Program Ranks

Common Scientific Federal NV NNPS Global State

FWS BLM

Alkali mariposa lily Calochortus striatus S,N,C W 2 1

Spring-loving centaury Centaurium namophilum T S F T 2Q 2

Tecopa Bird’s-beak Cordylanthus tecopensis S,N,C T 2 2

Ash Meadows sunray Enceliopsis nudicaulis var.

corrugata

T S F T 2 2

Ash Meadows gumplant Grindelia fraxino-pratensis T S F T 2 2

Ash Meadows ivesia Ivesia kingii var. eremica T S F T 1-2Q 1-2

Ash Meadows blazingstar Mentzelia leucophylla T S F T 1Q 1

Amargosa niterwort Nitrophila mohavensis E S F E 1 1

Death Valley blue-eyed grass Sisyrinchium funereum T 2-3 1

Bigroot blue-eyed grass Sisyrinchium radicatum W 2?Q 1-2

Ash Meadows lady’s tresses Spiranthes infernalis T 1 1 Abbreviations: FWS (Endangered Species Act administered by U.S. Fish and Wildlife Service): E – endangered; T – threatened; BLM (U.S. Bureau of Land Management): S – special status or sensitive; W – watch list; N – Nevada; C – California; NV (state of Nevada): F – fully protected; NNPS (Nevada Native Plant Society): W – watch list: T – threatened; E - Endangered. Nevada Heritage Program Ranks (Global – worldwide; State – within Nevada): 1 – critically imperiled; 2 – imperiled; 3 – vulnerable; Q – taxonomic status in question; ? – rank uncertain.

Source: Bio-West 2011.

1.4 Ecological Impacts of Dam Removal

The removal of Crystal Dam would dramatically alter current aquatic habitats. Restoration would convert deeper, cooler, and open water currently stored in Crystal Reservoir back to a natural drainage leading to Lower Crystal Reservoir. Thus wildlife dependent on large areas of deep, cool water would lose an open water habitat component, while thermal spring-adapted species that survive and proliferate under shallow, flowing water conditions, would gain habitat.

Conversion of the artificial ditch system below Crystal Spring back to a naturalized meandering spring channel and an anastomosing complex of spring channels, and removal of the Crystal Dam and reservoir are restoration actions that aim to create habitats historically natural to this area and to preserve the many rare and endemic species of AHME. Warmer, flowing water conditions and connected saturated soil conditions form key habitat components that are necessary for multiple rare animals and plants of Ash Meadows to survive. For example, many of the aquatic species such as the Ash Meadows Amargosa pupfish, various springsnails, and other rare aquatic invertebrates are thermophilic and can only survive and reproduce in waters within a warmer temperature gradient. The native fish species of Ash Meadows, especially the Ash Meadows speckled dace, are adapted to lotic aquatic conditions. Many of the rare plant species of Ash Meadows are closely linked to alkali meadow areas near springs that contain saturated soils from surface or groundwater located at or just below the soil surface (Bio-West, Inc. 2011). Much of the flowing warm spring channel and connected wet meadow habitat was lost with the construction of Crystal Dam and the construction of an artificial irrigation ditch network.

Crystal Reservoir provides a rare open water habitat component in an arid desert environment;

however, in general, this artificial reservoir does not support great biological diversity, and its establishment allows for the perpetuation of undesirable sport fish introductions into the system. The deeper, open water in Crystal Reservoir provides cooler water habitat that has harbored non-native game fish species that are incompatible with native AHME focal fish species of conservation concern (Scoppettone, et al. 2012). Although the open water likely provides a limited resource for migrating and wintering waterfowl as indicated by past aquatic bird surveys that reveal higher numbers of American coot and lower numbers of various ducks on the refuge (Great Basin Bird Observatory 2009), Ash Meadows has not historically, nor does it presently, support significant numbers of waterbirds (Threloff 1992).

Shallow waterways and marshes, on the other hand, which would be created with restoration, would retain warmer water than deep reservoir areas and provide optimal habitat for thermal aquatic endemic species. Shallow water areas with saturated soils also support areas with higher insect productivity (Great Basin Bird Observatory 2010); (Threloff 1992), forming a foundation for greater biodiversity at higher trophic levels. Marshes and wet/alkali meadows are among Nevada’s most diverse and prolific wildlife habitats. They produce abundant populations of macroinvertebrates that fuel food chains, either through being consumed first by fish or directly by shorebirds and small water birds. Hundreds of thousands of shorebirds

Otis Bay Ecological Consultants Page 7 migrate north and south through Nevada annually and are dependent on these invertebrates for protein and to store fat reserves needed for sustained, long-distance flight. Many of Nevada’s conservation priority waterfowl species also use marshes and their shorelines for nesting, but shift to larger open water bodies for migration and wintering.

An “ideal” marsh for birds consists of approximately equal proportions of open water and emergent vegetation, and aquatic birds usually prefer emergent vegetation stands with patchy, open water inclusions (Great Basin Bird Observatory 2010). Small marshes in more arid areas like southern Nevada where marsh patches may be a critical resource for upland birds have high bird habitat value. In a landscape context, connectivity of marshes with other mesic habitats, including additional marshes, wet meadows, and riparian areas, is very desirable and should factor into conservation prioritization and restoration design.

Marsh complexes associated with nearby wetlands and riparian areas have significant landscape value for birds, many of which are most abundant where these different habitat types are juxtaposed. High-quality wet meadow habitat is characterized by dense, uninterrupted groundcover comprised of a diversity of grasses, sedges, rushes, and forbs. High plant species diversity maximizes foraging value for birds that feed on forbs, insects, or rodents.

Of the habitat types identified in the Nevada Comprehensive Bird Conservation Plan (Great Basin Bird Observatory 2010), marshes with permanent water and emergent vegetation support a greater number of conservation priority bird species than any other habitat type.

Thus, conversion of the existing ditch system to a naturalized spring stream channel flowing out into a marsh and meadow complex would benefit not just aquatic species that include native fish and invertebrates, but higher trophic level organisms that include many conservation priority bird species. Loss of the open reservoir may cause a decrease in numbers of waterbirds, but new foraging habitats provided by the marsh may likely attract not just migrating waterfowl, but shorebirds and insectivores as well.

Because removal of Crystal Reservoir would expose soils that are currently under water, dam removal could potentially create new areas for rare plant colonization. If exposed soils receive enough water from either groundwater or surface runoff, then rare plants that currently form a “hotspot” of activity downstream and south of Crystal Reservoir (Bio-West, Inc. 2011) may have a chance to expand existing populations. Restoration activities that recreate historic groundwater conditions will likely result in an increase of alkali meadow habitat on the refuge (Otis Bay, Inc. and Stevens Ecological Consulting 2006).

The Comprehensive Conservation Plan (CCP) that was developed for all of the refuges within the Desert National Wildlife Complex identified potential short- and long-term impacts of dam removal at Crystal Reservoir (US Fish and Wildlife Service 2009).

Potential short-term impacts of this project include:

Temporary ground disturbance during construction which may affect surface water hydrology and water quality.

Disturbance to native fish in the project area. Disturbance impacts can be potentially reduced by relocating fish from waters anticipated to be affected by reservoir removal to other suitable locations.

Potential long-term impacts of Crystal Dam removal include:

Improvements to water conditions as historic hydrology and native habitats are restored.

Improvements in habitat conditions for native plants, specifically Amargosa niterwort.

No negative impacts to native fish populations, which prefer stream and spring habitats.

Elimination of unauthorized fishing by removing the source of game fish.

Removal of non-native fish, which will benefit the native fish and invertebrate populations.

Benefits to aquatic and avian species.

As identified in the CCP, removal of Crystal Dam would reduce open water habitat on the refuge. Once the dam is removed, habitat restoration that involves restoring the natural hydrology of Crystal Spring and connected marsh-meadow areas could then be implemented for the benefit of rare species of conservation need (US Fish and Wildlife Service 2009).

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2 RESTORATION DESIGN

2.1 Hydrology of the Crystal Reservoir Drainage Basin

The drainage basin that naturally drains into the Crystal Reservoir area covers 4.8 square miles (shown in Figure 2-1). Most of the water that regularly fills Crystal Reservoir is diverted from Crystal Spring by irrigation ditches. Additional sources of water for Crystal Reservoir come from a natural drainage channel and possibly from groundwater or springs located under the reservoir (Lindon 2009). Evaporation and infiltration losses from this reservoir may be close to 1000 acre-feet per year (Lindon 2009).

Figure 2-1. The Crystal Reservoir drainage basin covers a 4.8 square mile area.

2.2 Crystal Reservoir Dam: Specifics

Crystal Reservoir Dam was constructed in 1971 across a naturally occurring drainage. The dam is a 5,500 foot long earthen embankment and reaches 27 feet high at its highest point (see Figure 2-2). The toe elevation of the dam is 2,159 feet and the dam crest reaches 2,186 feet.

The dam was constructed from homogenous materials excavated from within the reservoir basin and nearby sites. The deepest point in the reservoir is located at the northwest end. This deep hole in the northwestern corner of the reservoir is referred to in the following Crystal Reservoir Dam removal plans as the “borrow pit” (See Figure 2-3).

Figure 2-2. Crystal Reservoir Dam from northwestern end looking southeast, September 2012.

Crystal Reservoir has two spillways that allow water to exit during high-water conditions (See Figure 2-3). The primary spillway (at 2,181 feet elevation) can pass 250 cubic feet per second (cfs), and an emergency spillway (at 2,183 feet elevation) can pass up to 2,000 cfs (Lindon 2009). At the lower spillway level, the reservoir holds 1,480 acre-feet of water and has a surface area of 175 acres. At maximum capacity, the reservoir holds 1,968 acre-feet of water and has a surface area of 204 acres (Lindon 2009).

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Figure 2-3. The Crystal Reservoir Dam is a 27-foot tall embankment with a primary spillway capable of passing 250 cfs and an emergency spillway capable of passing 2,000 cfs. Water diverted from the Crystal Spring channel flows into Crystal Reservoir from the north, and a siphon pipe at the center of the dam releases water toward Lower Crystal Reservoir.

2.3 Project Design Overview

Restoration plans for the Crystal Management Unit include restoration of the historic Crystal Spring outflow channel, an action that would remove Crystal Reservoir’s water source. As Crystal Reservoir and its inflow ditches may be key components of the Crystal Spring Channel dewatering plan, Otis Bay, Inc. recommends that removal of the Crystal Reservoir Dam occur after the restoration of Crystal Spring Channel. Once the Crystal Spring Channel has been restored, the source of inflow water will have been removed from Crystal Reservoir, and the reservoir basin can be emptied of water.

After Crystal Reservoir has been dewatered and allowed ample time to dry, Otis Bay, Inc.

recommends that the Crystal Reservoir Dam be removed by excavation to natural topographic grade. Embankment material removed from the dam can be pushed into the borrow pit located at the northwest corner of Crystal Reservoir (see Figure 2-3), and excess fill blended into the shoulders of the former reservoir basin to restore natural topography. A natural drainageway that matches local topography and geomorphology should be excavated through the former reservoir sediment, to accommodate stormwater runoff or outflow from Bradford and/or other small springs located to the east. Grading plans for removal of the Crystal Reservoir Dam are included as Appendix A of this document.

2.3.1 Sediment Management and Toxicity Testing

Sediment removal and management is a concern in many dam removal projects, as reservoirs collect sediment over time. When large volumes of sediment erode quickly from former reservoir sites, sediment can aggrade in downstream channels and result in channel widening, bank erosion, increased flood stage, and/or alteration of aquatic habitats. Water turbidity can increase, degrading water quality, and headward erosion of sediment deposits may occur after dam removal (Lindon 2009). FWS may wish to conduct toxicity testing on sediments contained within the reservoir basin. Toxicity is a greater concern in larger basins with upstream agricultural or mining activity, however, due to past agriculture and mining activity in the area, Otis Bay, Inc. recommends toxicity testing of sediments at this site.

Bathymetric survey data for Crystal Reservoir shows very little sediment accumulation, thus dredging or mechanical sediment removal via excavator will not be necessary at this site.

Instead (assuming no problems with sediment toxicity), Otis Bay, Inc. recommends that remaining sediment be left in place. Embankment material removed from Crystal Reservoir Dam can be used to fill the deepest part of the reservoir (the borrow pit), and excess material will be spread around the shoulders of the former reservoir basin to blend into the natural topography and geomorphology. A naturalized drainage channel will be constructed through the former reservoir, and surrounding sediment should be stabilized in place and revegetated with native plants to prevent wind and water erosion from flushing sediment downstream after reservoir removal. Otis Bay, Inc. recommends revegetation with native plants and temporary irrigation through the first season, in order to improve survival rate of plantings and to control dust and sediment mobilization.

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2.3.2 Lowering the Dam Embankment

There are two options for breaching the dam:

1. Full removal of the embankment. Full removal of Crystal Reservoir Dam embankment would require full excavation of the Crystal Reservoir Dam to natural topographic grade.

The excavated embankment material would be placed on the shoulders of the canyon and in the deep borrow pit in the west side of the reservoir basin (this is the same area used in the partial removal). To fully remove the dam, an earthmoving contractor would have to excavate and place approximately 500,000 cubic yards of soil.

2. Partial removal of the embankment. Partial removal of the embankment would require excavation of the center part of the Crystal Reservoir Dam to the natural topographic grade, but the two sides of the dam embankment would be gently sloped. Instead of hauling material off-site, the remains of the excavated embankment material would be pushed upslope into the borrow pit in the northwestern corner of the former reservoir basin.

Excess material would be blended and re-graded to match surrounding topography. Otis Bay, Inc.’s recommendation is to partially remove the embankment, as this alternative will meet the Refuge’s objectives and save substantial money. Approximately 40% of the embankment material (189,000 cubic yards) would be removed under this alternative.

To partially remove the dam, an earthmoving contractor will have to excavate approximately 189,000 cubic yards of soil from Crystal Dam (see drawings in Appendix A). Bathymetric survey data shows a deep hole at the northwest corner of the reservoir basin (see Sheet 3 of the Grading Plan in Appendix A), which was presumably a borrow pit, or the original source of much of the material used to construct the dam. During dam removal, material from the earthen embankment would first be rolled upstream and pushed into the borrow site within the former reservoir. The borrow pit will be filled with approximately 12.5 feet of soil, raising the ground surface elevation from 2,157 feet to approximately 2169.5 feet.

The dam crest reaches 2,186 feet at maximum elevation, and would be lowered to 2,160 feet (a 26 foot decrease). After filling the borrow pit within the basin to the desired elevation, excess fill material will be blended into the shoulders of the former reservoir, overlaying sediment deposits on the sides of the reservoir canyon. No soil would be placed in the bottom (center) of the reservoir basin, where a channel resembling the historic drainage way will be restored (See the Crystal Reservoir Rehabilitation Grading Plan shown on Sheet 6 of Appendix A).

By placing dam embankment material upstream into Crystal Reservoir, the material can be used to stabilize sediment deposits. Keeping the construction disturbance footprint confined to the inside of the former reservoir basin will ensure minimum disturbance to sensitive plants residing in the downstream marsh area. Remaining embankment fill material should be sloped as flat and wide as possible to prevent slope failures and to naturalize the setting.

2.3.3 The Spillway

Two spillways at Crystal Reservoir allow water passage during high-water conditions. The first spillway, a 15-foot wide spillway at 2,181 feet elevation, can pass 250 cfs. The 100-year flood at Crystal Reservoir was calculated to be 2,500 cfs. A second emergency spillway at 2,183 feet elevation is 650 feet wide and can pass 2,000 cfs. The combined spillway capacity along with reservoir storage routing capacity can therefore route the 100 year flow. The new channel through the basin should be constructed to pass a flood of this magnitude, and the attached design would fulfill this requirement.

2.3.4 Outlet pipe

Crystal Reservoir has two outlet pipes which siphon water over the dam. One is a 6” diameter pipe with 5 cfs capacity. The other is 12” pipe with 20 cfs capacity (Lindon 2009). In order to have a “no hazard” rating, there must be no operable outlet works at Crystal Reservoir following dam removal. Otis Bay, Inc. anticipates no problem with removing the outlet pipes, and recommends that the outlet works be removed completely after the reservoir dewatering process is complete.

Figure 2-4. Crystal Reservoir outlet pipes leading from reservoir across dam, September 2012.

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Figure 2-5. Crystal Reservoir outlet pipes leading from dam to Crystal Reservoir outflow channel, September 2012.

2.3.5 Restored Crystal Reservoir Drainage Channel

Toward the center of the former dam, a naturalized drainage (location based on 1984 aerial imagery) will be excavated, draining water from the east (Bradford Springs area) through the footprint of the former reservoir. Here, the dam will be lowered to an elevation of 2,160 feet (26 feet below its current elevation of 2186 feet). This breach would restore the natural drainage topography prior to the dam construction. The grading plan for the drainage way is shown on Sheet 6 of Appendix A.

2.4 Permits

Alterations to Crystal Reservoir will require the use of heavy machinery in a wetland area, thus federal and state permits such as NEPA, ACOE 404, NDEP 401, NDEP Working in Waterways, and NDEP Construction Stormwater permits will be necessary. The State of Nevada requires an “Application for Decommission, Breach or Removal of a Dam”, and/or a “Notice of Construction, Reconstruction, or Alteration of a Dam”. The US Fish and Wildlife Service (FWS) Dam Safety Office must approve the design as well (Lindon 2009).

3 CRYSTAL RESERVOIR CONSTRUCTION SEQUENCE

3.1 Construction Timing

Crystal Reservoir is fed by water diverted from the Crystal Spring channel. Removal of Crystal Reservoir Dam may occur before or after restoration of the Crystal channel, however, Otis Bay Inc. recommends restoring Crystal Spring channel first to remove the source of water that fills Crystal Reservoir. Dewatering of the reservoir basin should ideally occur at least three months prior to dam removal, to allow the site ample time to dry before construction begins.

The removal of Crystal Reservoir Dam should be completed in one season due to high risk of dam failure if a flash flood or storm were to occur prior to project completion. Otis Bay, Inc.

recommends that construction be scheduled for spring, summer or fall months, when conditions are driest.

3.2 Pre-Construction

3.2.1 Pre-Job Conference

Prior to equipment mobilization, the implementing contractor and FWS should hold a pre-job conference to coordinate between stakeholders, state and federal agencies, and other interested parties. The meeting will be used to review the project implementation and construction sequence, highlight refuge issues and concerns, explain procedures to avoid unnecessary impacts, delineate procedures to follow BMPs, and present expected final conditions. The pre-job conference will allow stakeholders to understand the work sequence, issue concerns, and request modifications to the implementation plan.

3.2.2 Collect and Move Native Aquatic Organisms and Rare Plants

At the discretion of AHME biologists, sensitive plants or wildlife located in areas downstream of Crystal Reservoir that may be affected by changes in water level during or after dam removal may be removed from the area prior to construction and relocated to appropriate habitat.

3.2.3 Construction Staking

Prior to mobilization, the contractor should identify and stake, flag, and fence cut/fill areas, staging areas, and locations of rare plant populations or other features to be protected. There are no known archaeological sites in close proximity to Crystal Reservoir. The staking should include establishing and marking grades along the dam. Refuge staff should agree to design plans and alignments after a site visit and prior to construction implementation.

3.2.4 Mobilization and Construction Access

Pre-construction activities should start with preparation of construction access points, staging areas, access roads, and mobilization of heavy equipment and supplies to the work site. If necessary, haul roads can be graded and vegetation cleared from within the construction footprint.

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A construction access map is shown in Figure 3-1. Access to Crystal Reservoir will be via the existing Crystal Loop Road and the top of the existing Crystal Reservoir Dam. Two small equipment staging areas will be located in existing parking areas close to the reservoir, where soils have already been disturbed. As the dam is removed, fill material will be pushed into the deepest part of the former reservoir basin (primarily the northwest corner). In this manner, the construction footprint will remain within existing disturbed areas, and disturbance to natural areas may be kept to a minimum.

Figure 3-1. Construction access map for Crystal Reservoir Dam removal.

3.3 Construction

3.3.1 Dewater Project Site

Prior to dam removal, Crystal Reservoir must be dewatered. The first step in dewatering the project site will be to remove the source of water inflow from Crystal Reservoir. The reservoir is fed by Crystal Spring. If Crystal Dam removal occurs before Crystal channel restoration, AHME will need to divert the inflow somewhere upstream of Crystal Reservoir. If Crystal Dam removal occurs after Crystal Channel restoration (recommended), the source of inflow water will have already been diverted.

The second step in dewatering the project site will be to drain the reservoir basin. Crystal Reservoir can be dewatered via releases through existing siphon pipes, with additional portable pumps used as needed to completely empty the reservoir. Portable pumps should be placed close to the deepest part of the reservoir, at the northwestern end of the dam (shown in Figure 3-1). Water can be pumped over the dam and discharged toward Lower Crystal Reservoir.

Ideally, after emptying the reservoir basin, the site should be allowed to dry out for a minimum of three months. The FWS should measure soil moisture in the former reservoir basin prior to the beginning of dam removal to determine whether use of wetland construction pads will be necessary.

3.3.2 Removal of Outlet Siphon Pipes

After dewatering the Crystal Reservoir basin, the outflow siphon pipe can be removed from the embankment using a large excavator, and properly disposed of. The location of the outflow siphon pipe is shown in Figure 3-1.

3.3.3 Removal of Crystal Dam

Otis Bay, Inc. recommends that the Crystal Reservoir Dam be removed in two phases: Phase 1, removal of material from the northwestern half of the dam (close to the borrow pit), and phase 2, removal of the southeastern half of the dam (farther from the borrow pit). Different equipment is recommended for each phase due to the distance that excavated dam material would need to be hauled to reach the borrow pit.

Phase 1: The first phase of dam removal (removal the portion of dam located closest to the borrow pit) should begin at the northwestern end of the proposed breach area of Crystal Dam, and proceed towards the center of the dam. Material should be excavated from the dam using a large dozer. The embankment should be pushed into the barrow pit area. The embankment should be lowered to the desired grade.

Phase 2: Once the northwestern portion of the embankment has been removed, work should proceed to the southeastern end of the embankment. Here, Otis Bay, Inc. recommends the use of scrapers to remove layers of dam and transport the remainder of the embankment material to the borrow pit and reservoir basin areas. A dozer (as used in Phase 1) would not be an efficient piece of machinery for transporting soil material over this distance, however, this work could also be accomplished via large excavator and haulpack dump trucks, depending on

Otis Bay Ecological Consultants Page 19 contractor preference. Work should proceed along the remainder of the dam from the southeast breach area to the northwest, lowering the embankment and transporting fill material into the borrow pit area until the embankment has reached the desired finish grade.

A total of 189,000 cubic yards of soil will be excavated from Crystal Dam and used to fill the borrow pit in the former reservoir basin. The borrow pit is expected to hold approximately 140,000 cubic yards of fill (about 75% of the material removed from the dam); the rest will be spread into the shoulders of the drainage (See Section 3.3.4). As the borrow pit is filled, excavated material should be spread using a large dozer, and sprayed with water at frequent intervals to control dust (see Section 5.4, Air Quality Control). The combination of water and dozer traffic should ensure adequate compaction of fill material in the former borrow pit.

Equipment recommendations are detailed in Section 4, Recommended Equipment.

3.3.4 Restore Natural Drainage Channel through Former Reservoir Basin

After filling the borrow pit in the northwestern portion of the former reservoir basin, approximately 50,000 cubic yards of leftover earthen fill material from the dam will be blended into the shoulders of the drainage. No soil should be placed down the center of the historic drainage; here, a natural drainage way will be restored to allow ephemeral flows or storm runoff to pass freely through to the marsh below. The grading plan for this natural drainage channel is shown on Sheet 5 of Appendix A.

3.3.5 Finished-Grading and Soil Decompaction

Upon completion of dam removal and placement of earthen fill, the area should be brought to finished-grade. A large dozer can be used to recreate natural topography (small hillocks, drainage ways, etc.). To promote vegetation recovery, all compacted and disturbed soils should be ripped, raked and graded, including access roads and stockpile areas.

3.4 Post-Construction

3.4.1 Site Cleanup

Any leftover construction material, old piping or other debris should be removed from the site and disposed of properly. BMPs such as fencing or flagging used to protect site features should be taken down and disposed of or stockpiled in an appropriate area.

3.4.2 Revegetation

Following construction, Otis Bay Inc. recommends that the former reservoir and dam site be revegetated with native plants by AHME. Mulch, seed and temporary irrigation may be necessary to establish vegetation. Intensive revegetation efforts will be important to prevent invasive species from taking over the bare soils and to control dust and sediment mobilization.

4 RECOMMENDED EQUIPMENT

The actions necessary for restoration at Crystal Reservoir will require construction crew and heavy machinery access. The primary activities will include dewatering, excavation and earthmoving. When working in wet conditions, Otis Bay Inc. recommends using equipment with tracks (rather than wheels). Additional equipment or modification of the equipment list shown below may be required following the completion of more detailed design and analysis.

Otis Bay, Inc. recommends that the following equipment be used for restoration construction at Crystal Reservoir:

Large Excavator – CAT 349 or equivalent (100,000 lb operating weight)

Large Dozer (Track-Type Tractor) – CAT D8T or equivalent (85,000 lb operating weight)

Scraper (Wheel Tractor-Scraper) – CAT 623 or equivalent (23 cubic yards heaped capacity)

Off-Highway Dump Truck – CAT 770 Haul Pack or equivalent (40-ton capacity)

Water Truck – 2000 gallon water truck for dust control

Wetland Pads

Portable pumps

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5 MEASURES TAKEN TO MINIMIZE IMPACT

5.1 Protection of Vegetation and Sensitive Species

The contractor should continually monitor for wildlife presence and minimize interference with and disturbance to wildlife at Crystal Reservoir. Several species of federally threatened and endangered plants occur in the vicinity of the work area (see Figure 3-1). Every effort should be made to minimize disturbance to threatened and endangered species on the job site.

Recommended steps to protect vegetation and sensitive species include:

Equipment and human access zones should be delineated using fencing and flagging.

Prior to the commencement of work, contractor should mark the boundaries of work areas and locations of rare plants, nests, sensitive habitat, archaeological resources and/or other features to be preserved with flagging or orange construction fence.

All equipment entering and leaving work sites should be inspected and cleaned to avoid transporting weeds, insects, or disease on or off site.

A FWS biologist should monitor all activities completed in the construction area.

Where possible, sensitive species may be salvaged from the construction area by a FWS biologist.

To promote vegetation recovery, soils within construction areas should be mechanically or manually de-compacted upon the completion of all construction activities.

5.2 Protection of Cultural Resources

No known cultural sites are located within the project area, however, any previously unknown cultural, historical, or archeological remains or items discovered during the Crystal Reservoir Dam removal project should be carefully preserved and the refuge manager should be notified.

Construction activity near artifacts should be avoided until required coordination with Federal, State, and Tribal agencies is complete.

5.3 Water Quality Control

The Crystal Reservoir dam removal project is not expected to impact the quality of surface waters at AHME, because the reservoir will be dewatered prior to construction and work will be done under dry conditions. No storage or stockpiling of equipment, tools or materials should occur within wetlands located downstream of the former reservoir basin. OBEC recommends the following methods to protect surface and groundwater during restoration activities at Crystal Reservoir:

Construction Planning

Stormwater Pollution Prevention Plan (SWPPP). A SWPPP detailing site BMPs for stormwater runoff pollution prevention must be developed and kept on site and up-to-date, as required under Nevada’s General Construction Permit. Site conditions to consider in the SWPPP include drainage patterns, slopes, areas of disturbance, location of BMPs, location of surface waters and wetlands, and location of stormwater drainage control points.

Preserve existing vegetation wherever possible. Existing vegetation should be preserved to the maximum extent possible, especially around the shoreline and reservoir outflow area. Digging and grading should be done only where necessary.

Native vegetation to be preserved should be protected by marking off a no-dig root protection zone with orange construction fencing. Before clearing vegetation or excavation begins, the required permits and erosion and sediment control BMPs should be in place.

Schedule project around local weather patterns. Excavation and grading should be done during dry weather, if possible. The contractor should plan for rainy weather by ensuring that erosion and sediment controls are in place and that soil stabilization measures are implemented on disturbed areas as quickly as possible. The project should be scheduled in order to limit the time and amount of bare soil exposed to weather.

Incorporate “Good Housekeeping Practices” at the work site. BMPs will be placed in appropriate locations to prevent pollutant discharge. Sanitary features such as portable toilets (if used) should be placed on bare soil and staked down so that they cannot be blown over by wind. All vehicle and equipment maintenance, fueling, and cleaning and storage should be done within the designated equipment staging area. Storage of construction materials, supplies, and waste will occur within the designated equipment staging area as well. The staging area will be regularly inspected for BMP effectiveness and hazardous material spills.

Employee awareness. All contractor employees should be made aware of good housekeeping practices and proper installation of BMPs. A copy of the SWPPP should be kept onsite, up-to-date, and available for review by all.

Construction Site Best Management Practices (BMPs)

Install BMPs before excavation, fill, or grading work begins. Fiber rolls, silt fences, and sediment barriers should be placed before clearing or excavation begins. Vegetated buffers of existing vegetation between construction areas and surface water should be left in place to filter runoff before it enters waterways.

Dust Control BMPs. Dust will be controlled by wetting haul roads and work areas as needed.

Divert upland runoff around areas of exposed soil. Low berms, silt fence, or fiber rolls can be placed on the upslope side of bare soil areas to prevent soil erosion by diverting runoff around exposed soil areas.

Place sediment barriers below bare soil areas. The contractor should use sediment barrier BMPs such as silt fence, sand bags, and fiber rolls on the downhill edge of bare soil areas (at the toe of slopes). Fiber rolls allow water to pass through but decrease runoff velocity, allowing sediment to settle out before reaching waterways.

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Protect slopes and channels from gullying. In the event of rainstorms or heavy surface runoff events, the contractor should use fiber rolls, silt fences, erosion control blankets, geotextile fabrics, or other methods to break up, trap, and slow down flows.

Protect wetland areas and stream channels. Silt fence should be placed along the edges of wetland areas to protect water quality from blowing dust and stormwater runoff. Vegetated buffers should be preserved wherever possible. In the event of rainstorms, fiber rolls may be used to prevent stormwater runoff from reaching water bodies.

Regular inspection and maintenance of BMPs. BMPs at the work site should be inspected and repaired every 7 days and after each rainfall event of 0.5” or more, according to state and federal regulations. Written records of repairs and maintenance of erosion and sediment control BMPs such as silt fences, vegetated buffers, berms, fiber rolls and other BMPs must be kept in writing, on the work site, as part of the SWPPP. Accumulated sediment from behind silt fences should be removed before it reaches ½ the silt fence height.

5.4 Air Quality Control

The Crystal Reservoir restoration project will involve use of heavy machinery. Dust may enter the air as a result of construction or vehicle traffic. The following steps are recommended in order to maintain air quality at Crystal Reservoir:

During all construction and ground disturbance activities, the contractor will monitor the conditions at the construction site and modify the dust-abatement effort according to the site conditions. Methods for reducing dust will include having a water truck on hand to control wind-born particulates.

Vehicles should be operated at reasonable speeds to keep dust to a minimum.

6 BEST MANAGEMENT PRACTICES (BMPS)

Before heavy equipment is brought on site, the contractor should work with refuge personnel to identify and mark features to be preserved, which may include: native plants (trees, shrubs, herbaceous plants and grasses), threatened and endangered species, landscape features (dune areas, upland or wetland plant communities), air and water quality, fish and wildlife (bird nests, fish or small mammal habitat), soil, and historical and cultural resources. Clear communication between the contractor and the client during this phase of the project will be essential in determining which features are to be preserved. The contractor will convey to all employees the importance of protecting sensitive site resources. Recommended methods for protecting these features include:

Flagging and Wire Pin Flags Brightly colored flagging and/or wire pin flags may be used to mark the locations of any endangered, threatened, state-listed, or otherwise sensitive species of plants found within a work area. Colored flagging and/or pin flags may also be used to denote locations of cultural or historical resources to be preserved and boundaries of work areas.

Marking Paint Marking paint may be used in combination with flagging and/or fences to indicate boundaries of work areas or habitat features.

Orange Construction Fence Orange construction fence may be used in combination with 4’ metal T-posts to create temporary barriers around features to be protected (such as sensitive plant communities), or to delineate edges of work areas. If larger patches of sensitive plants are located within a work area, orange construction fence may be used to create a barrier to prevent accidental disturbance. While heavy equipment is in use, orange construction fence may be used as a physical barrier to prevent pedestrian traffic (refuge visitors) from entering potentially dangerous areas.

Silt Fence Silt fence with wooden or metal posts may be used along the boundary of wetland areas and other areas as determined in field, to prevent stormwater runoff, soil, sediment, or other pollutants from reaching downstream water bodies.