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LOWER CRYSTAL DAM ()

Ash Meadows National Wildlife Refuge

Inspection Date: 11/14/2018

TABLE OF CONTENTS

CHAPTER Page

1. Current Conclusions 1

2. Current Recommendations and Cost Summary 3

3. Status of Previous Recommendations 7

4. Screening Level Risk Assessment 8

5. Pertinent Data 10

6. Inspection Checklist 17

7. Inspection and Project History 23

APPENDICES

A. Photos B. Figures, Maps and Plans C. Current Recommendations and Detailed Cost Data D. Supporting Documentation 2014 Seismic Hazard Map E. References

1. CURRENT CONCLUSIONS

A.

B.

1. Current Conclusions

Overall Safety Classification The overall safety classification of the dam is POOR.

POOR is defined by FWS as follows: A potential dam safety deficiency is recognized for unusual loading conditions that may realistically occur during the expected life of the structure. This term may also be used when uncertainties exist as to critical analysis parameters that identify a potential dam safety deficiency, i.e., further investigations and studies are necessary.

The reason for this rating is: Deficiency Recognized.

Lower Crystal Dam was in POOR condition due to the excessive vegetation on the upstream slope, dam crest, and downstream slope that prevent access or observation; excessive vegetation upstream and in the intake of the combined service spillway outlet works which will reduce the discharge capacity; and the dam/spillways not being capable of passing the 100-year flood with one-foot of residual freeboard.

Screening Level Risk Assessment The Screening Level Risk Assessment (SLRA) system for evaluating dams used by the FWS is a modification of the Bureau of Reclamation's SLRA method. The numeric total from the semi-quantitative method is used to rank a given dam with respect to the dam's downstream consequences and potential failure modes (normal, hydrologic, and seismic). The ranking factor total is unlimited based on the number of potential failure modes, with higher numbers being a worse condition. The

SLRA factors are assigned by the SEED inspector according to his or her evaluation at the time of the current inspection. The numeric total is used by the FWS to set priorities for repairs, studies, analyses, construction, and other dam safety activities.

The total SLRA value for this dam assigned during the current inspection is 68.

This is the initial SLRA score for Lower Crystal Dam. The score is based on the following key driving factors:

-The dam is located in an active seismic area (PGA>0.2g) and a liquefaction evaluation has not been performed.

-The dam does not have the ability to pass the 100-year flood with one-foot of residual freeboard;

overtopping is considered to be a very high likelihood.

-The combined service spillway and outlet works intake is plugged with vegetation reducing the capacity which is considered a very high likelihood that the dam could overtop prematurely.

-Static Potential Failure Modes for stability, seepage in the embankment/foundation, and seepage into

/ LOWER CRYSTAL DAM 1

C.

D.

E.

F.

G.

conduits were considered of high likelihood due to the unknown construction of the dam.

Hazard Classification The dam is classified as a LOW HAZARD dam.

If Lower Crystal Dam failed, the flood water would cross Stateline Road and continue into California.

A hazard classification was performed and recommended that Lower Crystal Dam be classified as a

Low Hazard Dam (Wheeler, 2019).

Hydrology and Hydraulics Review Lower Crystal Dam is an small sized, Low Hazard Dam which requires the dam to safely pass the

100-year flood. The 100-year flood was developed for the 6.72 square mile drainage basin by W. W.

Wheeler and Associates, Inc. for the 2019 Hazard Classification Evaluation (Wheeler, 2019). The 6.72 square mile drainage basin includes the contributing area to Crystal Lake Dam and Horseshoe Dam, both located upstream of Lower Crystal Dam. The 100-year precipitation was developed based on the depths and temporal distributions from NOAA Atlas 14 for a 24-hour storm, resulting in a 2.75-inch depth. The drainage basin contributing directly to Lower Crystal Dam consists of hydrologic soil type

"C" soils. The peak inflow into Lower Crystal Dam was 326 cubic feet per second (cfs) with a storm volume of 499 acre-feet. The reservoir routing of this storm event results in a maximum water surface

Elevation of 2146.0 feet, which provides 0.0 feet of freeboard to the dam crest. The hydrology was developed assuming the discharges from Crystal Springs Dam and Horseshoe Dam are directly input into Lower Crystal Reservoir, without channel routing.

According to the Refuge Manager, a 500-year flood event occurred on Ash Meadows National

Wildlife Refuge in October 2015. Erosion was not observed in the spillways as a result of this event;

however, the Refuge did not provide documentation of the water level or spillway discharges as a result of this event.

Seismicity Review The 2014 USGS update of the United States National Seismic Hazard Map, provided in the

Supporting Documentation, indicates that the peak ground acceleration associated with a 2-percent probability of exceedance in 50 years is 0.3 to 0.4 g at the dam site.

Geologic and Geotechnical Review There is no known design information to perform a geologic and geotechnical review.

Civil and Structural Review There is no known design information to perform a civil and structural review.

/ LOWER CRYSTAL DAM 2

2. CURRENT RECOMMENDATIONS AND COST

SUMMARY

2. Current Recommendations and Cost Summary

Year of Estimate: 2018

A. Emergency Situation

B. Maintenance

C. Operations and Monitoring

D. Construction

Recommendation(s) Cost None

Total Emergency Situation Recommendations 0 Total Emergency Situation Costs $0.00

Priority 1 Recommendation(s) Cost

1. (2018-1MA-01) Mow the upstream slope, crest, and downstream slope of the embankment for a distance of 20 feet downstream of the downstream toe to maintain grass at a reasonable height to allow for proper inspection and monitoring of the embankment and to deter burrowing animals. The grass vegetation should be removed from the intake structure for the combined service spillway and outlet works.

$9,991.35

P1 Maintenance Recommendations 1 P1 Maintenance Costs $9,991.35

Priority 2 Recommendation(s) Cost None

P2 Maintenance Recommendations 0 P2 Maintenance Costs $0.00

Total Maintenance Costs $9,991.35

Priority 1 Recommendation(s) Cost None

P1 Operations and Monitoring Recommendations 0 P1 Operations and Monitoring Costs $0.00

Priority 2 Recommendation(s) Cost

1. (2018-2OM-01) On a monthly basis visually monitor the ditch near Station 18+40, and visually monitor for soft soil deposits at the downstream toe of the embankment (such as what was observed near Station 16+00 during the 2018 SEED Inspection). Look for signs of changing seepage patterns and flow including boils, increased flow, or cloudy discharge. Contact the Regional Dam Safety Officer if any of these conditions are observed.

$0.00

P2 Operations and Monitoring Recommendations 1 P2 Operations and Monitoring Costs $0.00

Total Operations and Monitoring Costs $0.00

/ LOWER CRYSTAL DAM 3

E. Additional Studies or Analyses

F. Future Inspections

Priority 1 Recommendation(s) Cost

1. (2018-1CO-01) Design and construct dam safety modifications to safely pass the inflow design flood with one-foot of freeboard, consistent with FWS dam safety policy.

$137,060.09

P1 Construction Recommendations 1 P1 Construction Costs $137,060.09

Priority 2 Recommendation(s) Cost

1. (2018-2CO-01) Consider breaching the dam to remove it from the US Fish & Wildlife Service Inventory. Consultation with the Regional Dam Safety Engineer is required to ensure that the dam is removed in accordance with the US Fish & Wildlife Service Standards. If this recommendation is implemented, the other recommendations will not be required.

$151,543.42

P2 Construction Recommendations 1 P2 Construction Costs $151,543.42

Total Construction Costs $288,603.50

Priority 1 Recommendation(s) Cost

1. (2018-1SA-01) Perform Title 1 engineering services to design dam safety modifications to safely pass the inflow design flood, consistent with FWS dam safety policy.

$27,891.00

P1 Additional Studies or Analyses Recommendations 1 P1 Additional Studies or Analyses Costs $27,891.00

Priority 2 Recommendation(s) Cost

1. (2018-2SA-01) Evaluate the dam decommissioning requirements and design the potential dam modifications needed to breach the dam consistent with FWS dam safety policy.

$111,564.00

2. (2018-2SA-02) Consider performing a field survey or drone survey of the State Line Road to validate the hazard classification and the assumptions from the December 2019 Hydrology and Hazard Classification Evaluation.

$6,655.77

P2 Additional Studies or Analyses Recommendations 2 P2 Additional Studies or Analyses Costs $118,219.77

Total Additional Studies or Analyses Costs $146,110.78

Recommendation(s) Cost

1. (2018-1FI-01) It is recommended that the grasses on the embankment be mowed prior to the next inspection so the entire embankment can be observed.

$0.00

Total Future Inspections Recommendations 1 Total Future Inspections Costs $0.00

Total Emergency Recommendations 0 Total Emergency Costs $0.00

Total P1 Recommendations 3 Total P1 Costs $174,942.44

/ LOWER CRYSTAL DAM 4

Definitions

The U.S. Fish and Wildlife Service (FWS) has established the following categories to determine a priority ranking system for which work must be completed in order to maintain the integrity and operation adequacy of dam structures:

Emergency Situation - Structure is in danger of imminent failure and action must be taken immediately to alleviate the emergency.

Priority 1 (P1) - Normal condition of the structure is impaired and the safety of the structure is in jeopardy.

Priority 2 (P2) - Conditions do not currently appear to threaten the safety of the dam. Continued deterioration and/or unusual loading may threaten the safety of the dam.

Total P2 Recommendations 4 Total P2 Costs $269,763.19

Total Future Inspection Recommendations 1 Total Future Inspection Costs $0.00

Total Recommendations 8 Total Costs $444,705.62

/ LOWER CRYSTAL DAM 5

Table 4-1 Operations Schedule Lower Crystal Dam

W ee kl y

M on th ly

Q ua rt er ly

Se m i-A nn lly

A nn lly

E ve ry

Y ea rs

E ve ry y ea rs

O cc as io na l

O cc ur re nc e

Responsible Entity

R ef ug e

M an ag er

R D

SO

SD

SO

STANDING OPERATION

Operations Dam Visit B(1)

Transmit Log & Forms Flood Operations B B Instrumentation Reservoir Staff Gage B,A Inspection Station Inspection(2) B,C SEED Inspection (3) B Special Inspection(4) B,C

Interior Pipe Inspections (5)

Maintenance Control Vegetation (6) B

Maintain Stoplogs & Hoist Per Manufacturer’s Recommendation B

General Maintenance B Unusual or Emergency Event Emergency Action B

Shading indicates responsible entity.

(1) Letters indicate forms used for respective activity. Forms can be found in the Low Hazard SOP:

A Form 2a B Form 1a - Operations Log C Form 1b – Intermediate Inspection Checklist for Low Hazard Dams

(2) Items to look for during monthly inspections are outlined in Chapter 2 of the Low Hazard SOP and should be documented on Form 1b. Items to pay special attention to during monthly inspections include monitoring for erosion on the embankment slopes; sediment deposits at the downstream toe; corrosion or continued deterioration of the combined service spillway/outlet works conduit; and vegetation growth or vegetation causing flow restrictions at the spillway. IN PARTICULAR, THE DAM SHOULD BE

INSPECTED DURING HIGH WATER STORAGE LEVELS FOR SEEPAGE.

(3) Alternate Formal SEED Inspection and Intermediate SEED Inspection every 5 years.

(4) Items to look for during special inspections are outlined in Chapter 2 of the Low Hazard SOP and should be documented on Form 1b. Special inspections should be performed after a significant flood or an earthquake.

(5) The discharge pipe for the combined service spillway/outlet works should have an interior pipe inspection performed as needed.

(6) At least twice during growing seasons.

3. STATUS OF PREVIOUS

RECOMMENDATIONS

3. Status of Previous Recommendations

There are no previous recommendations for this dam.

/ LOWER CRYSTAL DAM 7

4. SCREENING LEVEL RISK ASSESSMENT

Dam Name: Lower Crystal Dam NID No.: NV10341 Station: Ash Meadows National Wildlife Refuge Region: 8 Hazard Classification: Low (pending 2019 Hazard Classification) Dam Type: Earthfill Dam Height: 6.1 feet Maximum Storage: 296 acre-feet

Low Hazard Screening Level Risk Matrix

Extremely High (greater than 1E-02 or less than 100yr)

Very High (1E-03 to 1E-02 or 1,000yr to 100yr)

High (1E-04 to 1E-03)

Moderate (1E-05 to 1E-04)

Low (1E-06 to 1E-05)

Consequence Level

Total SLRA Risk Score: 68

Static - Stoplog failure

Hydrologic - Overtopping Hydrologic - Operations

30 100

1 3

Static - Stability

Static - Seepage Emb/Found Static - Seepage - Conduit

10 30

0 1 3 5 10

0 0 1 3 5

Li ke lih oo d

8 10

Seismic - Liquefaction

0 1 2 3 4

/ LOWER CRYSTAL DAM 8

Consequences: Level 0

Level 2

Failure Modes:

Likelihood Consequences Score

High 2 5

High 2 5

High 2 5

Very High 0 3

Very High 2 10

Very High 2 10

Extremely High 2 30

Static Potential Failure Modes Structure instability (static), resulting in failure of the dam. Slopes about 3H:1V and no known adverse conditions. FS unknown. Construction materials unknown, soils appear to be erodible materials.

Damage to the structure and the resource it provides (pool/habitat) and/or FWS property that would not impact the mission of the Station/Service and would not require repair.

In the case of a dam failure associated with the potential failure modes, expected consequences include moderate damage to the structure and the resource it provides (pool/habitat); however, the Refuge intends to remove the dam in the future because it does not provide value to their habitat mission; inundation of the Refuge property; and inundation of State Line Road located downstream with a traffic count in excess of 400 vehicles per day and is paved. A hazard classification was authorized in 2019 to evaluate the consequences of a dam failure.

Description Reason

Gate deterioration/failure and/or misoperation, resulting in uncontrolled releases (ie, pin friction, lack of maintenance).

Stoplog structure with restricted access due to vegetation encroachment on the upstream inlet of the riser structure. Infrequent or inconsistent maintenance and operation.

Seepage along/into conduits/drains, resulting in internal erosion/piping.

No observed piping or seepage along or into conduit/drain. Accessible. Construction methods unknown. Minor corrosion observed in the CMP conduit. Vegetation at upstream intake could initiate a path.

Seepage through the embankment/foundation, resulting in internal erosion/piping.

No observed piping or seepage during 2018 SEED inspection; however, dam was only impounding about 1-foot of water. Construction methods unknown. Drainage ditch near Station 18+40 could convey seepage downstream of the dam (dry at time of inspection).

Discharge/release capacity is reduced or inoperability / misoperation of gates, resulting in premature overtopping(ie, debris, high tailwater, high reservoir levels, fish screens, loss of power / access / communication, ASR, mechanical failure).

Controls unreliable due to vegetation; service spillway/outlet works capacity restricted by vegetation. Infrequent or inconsistent maintenance and operation.

Hydrologic Potential Failure Modes Erosion of embankment dam due to overtopping, resulting in breach of the reservoir.

Dam and appurtenances can accommodate the 100-yr flood, with no freeboard. Dam overtopped by the 1,000-yr flood.

Seismic Potential Failure Modes Liquefaction of embankment/foundation materials, resulting in deformation, loss of freeboard, cracking/separation, or structural failure.

Located in active seismic area (PGA > 0.2g) and unknown embankment/foundation materials. Not designed for EQ loading.

/ LOWER CRYSTAL DAM 9

5. PERTINENT DATA

A.

B.

5. Pertinent Data General

Dam Section(s)

1. Dam Name *: LOWER CRYSTAL DAM

2. NID Number *:

3. Other Dam Name(s) *: Lake Number 7

4. Dam Former Name(s) *:

5. Dam State *: NV

6. Dam County *: NYE

7. Dam Latitude *: 36.39

8. Dam Longtitude *: -116.33

9. Legal Description (Section, Township, Range Location) *:

S10&15, T18S, R50E

10. River or Stream Name *: Carson Slough - TR

11. Basin: Amargosa River

12. Reservoir Name: Lake Number 7

13. Year Constructed *:

14. Year and Reason Dam Modified *:

15. Downstream Hazard Potential Classification *: LOW

16. Resource Value: Secondary Resource

17. Inventory Status: Inventory

18. Size Classification: SMALL OR MINOR

19. SAMMS#: 10005161

20. Confined Space: yes

21. Estimated Economic Losses Downstream: < $ 1 million

Notes:

Item No. 2: NID number is NV10341 based on the NID database. Nevada has two dams associated with this structure including:

Crystal Marsh Lower Dam, State ID: J-477, NID: NV10540 Crystal Marsh Upper Dam, State ID: J-476, NID: NV10539 Item Nos. 13 and 14: No construction information available. NID database does not include a year complete date.

Embankment Dam Section 1: MAIN EMBANKMENT

1. Dam Type *: EARTH

2. Crest Elevation: 2,146 Ft.

3. Dam (Crest) Length *: 290 Ft.

4. Crest Width: 25 Ft.

5. Dam Height *: 6.1 Ft.

6. Structural Height *: 6.1 Ft.

7. Hydraulic Height *: 6.1 Ft.

8. Upstream Slope: 2.5 H:1V to 4.5 H:1V

9. Downstream Slope: 2.5 H:1V to 3 H:1V

/ LOWER CRYSTAL DAM 10

10. Core Position *: UNLISTED/UNKNOWN Type *: UNLISTED/UNKNOWN Certainty *:

11. Foundation *: UNLISTED/UNKNOWN Certainty *:

Karst:

12. Volume of Dam *: 2,777 CY

Notes:

Dimensions based on 2007 LiDAR data (FWS, 2007) and measurements from the 2018 SEED Inspection.

Item No. 3: This portion of the embankment extends from Dam Station 2+60 to 5+50.

Item No. 5: The dam height is based on the vertical distance between the lowest point on the dam crest and the lowest point in the original streambed. The lowest point in the original streambed was based on a hand level measurement from the dam crest to the downstream invert of the outlet pipe for the combined service spillway/outlet works structure, Elevation 2139.9.

Item No. 6: The structural height is based on the vertical distance between the lowest point on the dam crest and the lowest point of the excavated foundation, which was assumed to be the downstream invert of the outlet pipe.

Item No. 7: The hydraulic height is based on the vertical distance between the maximum design water level and the lowest point in the original streambed; El. 2146.0 - El. 2139.9 =

6.1 feet. The lowest point in the original streambed was determined in the field during the 2018 SEED Inspection. The hydrologic analysis concluded that the 100-year event would result in a water surface elevation of 2146.0 (Wheeler, 2019).

Item No. 12 - The volume of this section of the dam was estimated assuming a consistent section extends from the left abutment to the right abutment. Using a cross sectional area of

258.5 SF (assuming height = 6.1 feet, crest width = 25 feet, upstream slope = 3.0H:1V, downstream slope = 2.7H:1V). Volume of dam = 258.5 SF * 290 feet = 2,777 CY.

Embankment Dam Section 2: RIGHT EMBANKMENT

1. Dam Type *: EARTH

2. Crest Elevation: 2,146 Ft.

3. Dam (Crest) Length *: 2,005 Ft.

4. Crest Width: 10 Ft.

5. Dam Height *: 6 Ft.

6. Structural Height *: 6 Ft.

7. Hydraulic Height *: 6 Ft.

8. Upstream Slope: 3.5 H:1V to 4 H:1V

9. Downstream Slope: 3.5 H:1V to 4 H:1V

10. Core Position *: UNLISTED/UNKNOWN Type *: UNLISTED/UNKNOWN Certainty *:

11. Foundation *: UNLISTED/UNKNOWN Certainty *:

Karst:

/ LOWER CRYSTAL DAM 11

C.

D.

Saddle Dike(s)

Discharge Structure(s)

12. Volume of Dam *: 14,481 CY

Notes:

Dimensions based on 2007 LiDAR data (FWS, 2007) and measurements from the 2018 SEED Inspection.

Item No. 4: The lowest point on the dam crest is Elevation 2146.0 based on the LiDAR data.

The dam crest elevation varies, with the dam crest from about Station 12+80 to 18+30 ranging from about Elevation 2146 - 2147. Near the right abutment the dam crest Elevation is 2150 - 2151.

Item No. 3: This portion of the embankment extends from Dam Station 12+80 to 32+85.

Item No. 5: The dam height is based on the vertical distance between the lowest point on the dam crest and the lowest point in the original streambed. The lowest point in the original streambed was based on LiDAR data at the downstream toe. Elevation 2146 - Elevation 2140 = 6.0 feet.

Item No. 6: The structural height is based on the vertical distance between the lowest point on the dam crest and the lowest point of the excavated foundation, which was based on LiDAR elevation data at the downstream toe. Elevation 2146 - Elevation 2140 = 6.0 feet.

Item No. 7: The hydraulic height is based on the vertical distance between the maximum design water level and the lowest point in the original streambed; El. 2146.0 - El. 2140 = 6.0 feet. The hydrologic analysis concluded that the 100-year event would result in a water surface elevation of 2146.0 (Wheeler, 2019).

Item No. 12 - The volume of this section of the dam was estimated assuming a consistent section extends from the left abutment to the right abutment. Using a cross sectional area of 195 SF (assuming height = 6.0 feet, crest width = 10 feet, upstream slope = 3.75H:1V, downstream slope = 3.75H:1V). Volume of dam = 195 SF * 2005 feet = 14,481 CY.

There are no saddle dikes currently associated with this structure.

Discharge Structure 1: EMERGENCY SPILLWAY at DAM STATION 0+00

1. Discharge Structure Type: Emergency Spillway

2. Description: Trapezoidal Earth Channel

3. Location: Station 0+00

4. Approach Channel: Unlined Earth Channel

5. Intake Structure: Broad-Crested Weir Section

a. Crest Elevation: 2,145.5 Ft.

b. Invert Elevation: Ft.

c. Size:

d. Material: Earth

e. Width: 10 Ft.

6. Control Structure: None

a. Type *: UNCONTROLLED

b. Min Control Elevation: Ft.

c. Max Elevation of Gate Opening: Ft.

d. Max Control Elevation: Ft.

/ LOWER CRYSTAL DAM 12

e. Size:

f. Material:

7. Conveyance Structure: Unlined Earth Channel

a. Length: 150 Ft.

b. Size:

c. Inlet Invert Elevation: Ft.

d. Outlet Invert Elevation: Ft.

e. Year of Conduit Installation:

8. Outlet Structure: None

a. Energy Dissipation: None

9. Discharge Channel: Discharges to downstream pool

10. Discharge Capacity with Water Surface at *: Top of Dam : 9.2 cfs and is based on the following formula: Q=C*L*H^1.5

Notes:

Dimensions updated based on LiDAR data (FWS, 2007) and measurements collected in the 2018 SEED Inspection.

Item 10: The discharge capacity of the emergency spillway can be estimated using the following formula; Q=C*L*H^1.5, where H = water surface elevation - spillway crest elevation, C = 2.6, L=10 feet. At the dam crest (EL 2186), discharge = 2.6*10*(2146- 2145.5)^1.5 = 9.2 cfs.

Discharge Structure 2: Combined Service Spillway/Outlet Structure at Dam Station 4+40

1. Discharge Structure Type: Combined Service Spillway and Outlet

Works

2. Description: CMP Riser with stoplog slots and wood wingwalls

3. Location: Station 4+40

4. Approach Channel: Reservoir

5. Intake Structure: Half-round CMP riser with stoplog control

a. Crest Elevation: Ft.

b. Invert Elevation: 2,140 Ft.

c. Size: 3-foot-diameter CMP

d. Material: CMP

e. Width: 3 Ft.

6. Control Structure: Stoplog Control

a. Type *: CONTROLLED

OTHER CONTROLLED

b. Min Control Elevation: 2,140 Ft.

c. Max Elevation of Gate Opening: Ft.

d. Max Control Elevation: 2,145 Ft.

e. Size: 3-foot-wide stoplog slots

f. Material: wood

7. Conveyance Structure: 3-foot-diameter CMP

a. Length: 50 Ft.

/ LOWER CRYSTAL DAM 13

E. Reservoir / Flood Hydrology

b. Size: 3-foot-diameter

c. Inlet Invert Elevation: 2,140 Ft.

d. Outlet Invert Elevation: 2,139.9 Ft.

e. Year of Conduit Installation:

8. Outlet Structure: Plunge Pool

a. Energy Dissipation: Unlined Plunge Pool

9. Discharge Channel: Downstream pond

10. Service Spillway Discharge Capacity with Water Surface at *: Top of Dam : 62.4 cfs and is based on the following formula: Culvert Master Calculation Outlet Works Discharge Capacity with Water Surface at: Top of Dam : 62.4 cfs and is based on the following formula: Culvert Master Calculation

Notes:

Dimensions updated based on LiDAR data (FWS, 2007) and measurements collected in the 2018 SEED Inspection.

Item 10: The discharge capacity is controlled by the 3-foot-diameter CMP discharge conduit.

Discharge was calculated using Culvert Master and provided in Wheeler, 2019.

Reservoir Storage Level Elevation (feet) Surface Area

(acres) Capacity (acre-feet)

Maximum Normal Pool * 2,143 61.6 76.4 Discharge Structure 1:

EMERGENCY SPILLWAY

at DAM STATION 0+00

2,145.5 111.4 249.4

Discharge Structure 2:

Combined Service Spillway/Outlet Structure at Dam Station 4+40

2,140 0 0

Top of Dam * 2,146 121.3 296

Flood Hydrology

1. Inflow design flood: 100-year storm

2. Storm Duration: 24 hours

3. Total Rainfall: 2.75 inches

4. IDF Peak Inflow: 292 cfs

5. Storm Volume: 497 acre-feet

6. Max. reservoir water surface elevation during the IDF:

2,146 Ft.

7. IDF Freeboard: 0 Ft.

8. Depth of Overtopping:

0 Ft.

9. Duration of Overtopping:

0 hours.

10. IDF Peak Outflow: 71.8 cfs

11. Drainage Area: 6.72 square miles

12. Drainage Basin Description *:

Armagosa Valley closed basin

Notes:

The maximum normal pool is 3 feet below the dam crest.

Item 11: Total contributing drainage area is 6.72 square miles including drainage basins for upstream dams; Crystal Springs Dam and Horseshoe Dam. No channel routing was assumed

/ LOWER CRYSTAL DAM 14

F.

G.

H.

Management

EAP / SOP

Inspection Details for the discharges from Crystal Springs Dam or Horseshoe Dam to Lower Crystal Dam.

1. Owner Name *: US FISH AND WILDLIFE SERVICE

2. Owner Type *: FEDERAL

3. Dam Designer *: Chuck Armuth

4. Private Dam on Federal Property *: no

5. Field Station: Ash Meadows National Wildlife Refuge

6. Dam Purposes *: FISH AND WILDLIFE POND

7. Field Station Contact Information:

Name: Corey Lee Address1: 610 E. SPRING MEADOWS ROAD Address2: AMARGOSA VALLEY, NV 89020 Phone: (775) 372-5435

8. Dam Safety Program Contact:

Name: Zach Spruell

Regional Dam Safety Officer, Region 8 Address: Region 1 7 8 Division of Engineering

911 NE 11th Avenue (3W) Portland, OR 97232

Phone: (503) 231-2396

9. Organization Code: 84554

10. Region: 8

11. Ecosystem:

12. Federal Agency Involvement in Design *:

13. Federal Agency Involvement in Construction *:

14. Federal Agency Involvement in Regulatory *: U.S. Fish and Wildlife Service

15. Federal Agency Involvement in Inspection *: U.S. Fish and Wildlife Service

16. Federal Agency Involvement in Operation *: U.S. Fish and Wildlife Service

17. Federal Agency Owner *: U.S. Fish and Wildlife Service

18. Federal Agency Involvement - Other *:

Notes:

Item 3: Information from the NID Database.

Item 14: The NID database indicates that the dam was initially privately owned by Nye County Land Company.

1. Emergency Action Plan (EAP): * not required

Notes:

Not required.

1. Date of Previous Inspection:

Inspection Type:

/ LOWER CRYSTAL DAM 15

I. Pertinent Data Notes The elevations are based on the LiDAR data (FWS, 2007), NAVD88.

* denotes data submitted to the NID.

2. Date of Most Recent Inspection *: 11/14/2018 Inspection Type: Formal

3. Inspection Frequency *: 5 Est. Date of Next Inspection: 11/14/2023

4. Inspected By (Primary): Danielle Tripp Hannes, P.E., Associate

Engineer, W. W. Wheeler and Associates, Inc.

Inspected By (Secondary): Andrea Fasen, P.E., Water Resource Engineer, W. W. Wheeler and Assoicates

5. Reviewed By: Ying-Kit Choi, P.E., Technical Reviewer, W. W. Wheeler and Assoicates, Inc.

6. Prepared By: W.W. Wheeler and Associates, Inc.

7. Date of Most Recent Internal Inspection:

None

Notes:

Item 2: The 2018 SEED Inspection is the initial inspection of Lower Crystal Dam.

Item 7: It is unknown if an internal inspection has ever been performed for the combined service spillway/outlet works pipe.

/ LOWER CRYSTAL DAM 16

6. INSPECTION CHECKLIST

[Lower Crystal Springs Dam (Lake No. 7), Ash Meadows NWR] Page 1

INSPECTION CHECKLIST FOR LOW HAZARD DAMS

DAM NAME: Lower Crystal Dam (Lake No. 7) DATE INSPECTED: November 14, 2018

NID NO.: NV10341; NV Inspection Reports: NV10539 & NV10540 DATE OF PREVIOUS INSPECTION: N/A STATION: Ash Meadows National Wildlife Refuge WEATHER/TEMP.: Sunny, 50°F

COUNTY/STATE: Nye County, Nevada POOL ELEVATION: 2142.0(stoplogs); Staff gage = 2.1 feet

HAZARD CLASSIFICATION: LOW TAILWATER ELEVATION: 2141.0

INSPECTED BY: Danielle Hannes P.E. and Andrea Fasen E.I., W.W. Wheeler and Associates, Inc.

CHANGE IN INVENTORY STATUS: Inventory Non-inventory No Change

UPSTREAM SLOPE – EMBANKMENT – Main Embankment from Station 2+60 to 5+50;

and Right Embankment from Station 12+80 to 32+85

PROBLEMS NOTED: (1) None (2) Excessive vegetation (3) Animal burrows

(4) Wave erosion; with scarps (5) Appears too steep (6) Depressions or bulges

(7) Sinkholes (8) Cracks; with displacement (9) Slides (10) Concrete facing:

holes; cracks; displacement; undermined (11) Slope protection: missing; sparse; displaced;

weathered (12) Other

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

(2) Excessive grass vegetation that was greater than about 6 feet in height was observed on the entire upstream slope from Station 2+60 to 5+50 and from Station 12+80 to 17+65 (see Photo Nos. 1 – 4). From Station 17+65 to Station 32+85, the upstream slope was not able to be accessed due to the 6-foot-tall thick grass vegetation that was also on the dam crest and downstream slope (see Photo No. 7).

(12) Due to the vegetation, visual observation and inspection of the upstream slope was not possible.

PHOTOS: The upstream slope is shown on Photo Nos. 1 – 4, and 7.

CREST – EMBANKMENT – Main Embankment from Station 2+60 to 5+50; and Right Embankment from Station 12+80 to 32+85

PROBLEMS NOTED: (1) None (2) Excessive vegetation (3) Animal burrows

(4) Erosion (5) Sinkholes (6) Cracks; with displacement (7) Ruts or puddles

(8) Inadequate surface drainage (9) Not wide enough (10) Misalignment

(11) Low areas (12) Other

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

(2) Excessive grass vegetation that was greater than about 6 feet in height was observed on the dam crest from approximate Sta. 17+65 to 32+85, which prevented visual observation and inspection. See Photo No. 7.

(11) The dam crest elevation varied based on field observations and LiDAR data resulting in areas of the dam crest being lower than other areas. The main embankment was observed to be relatively consistent at Elevation 2146 from Station 2+60 to 5+50.

The right embankment ranged in elevation from about 2146 to 2147 from Station 12+80 to 18+30, with the dam crest elevation increasing near the right abutment with the Elevation around 2151 near Station 32+85.

(12) Due to the presence of vegetation, it was not possible to discern in the field where the Right Embankment ended. The right abutment of the Right Embankment was approximated using LiDAR topography at Sta. 32+85. See Photo No. 7.

(12) A topographically high natural area exists from Station 5+50 to 12+80 that was not considered to be part of the dam embankment. See Photo Nos. 8 and 9.

PHOTOS: The dam crest is shown on Photo Nos. 1, 2, 5 - 7. Photo Nos. 8 and 9 show the natural high topographic area between the Main Embankment and Right Embankment.

/ LOWER CRYSTAL DAM 17

[Lower Crystal Springs Dam (Lake No. 7), Ash Meadows NWR] Page 2

DOWNSTREAM SLOPE – EMBANKMENT – Main Embankment from Station 2+60 to 5+50;

and Right Embankment from Station 12+80 to 32+85

PROBLEMS NOTED: (1) None (2) Excessive vegetation (3) Animal burrows

(4) Erosion or gullies (5) Appears too steep (6) Depressions or bulges

(7) Sinkholes (8) Cracks; with displacement (9) Slides (10) Slope protection:

missing; sparse; displaced; weathered The presence of vegetation prevented a complete inspection for problems such as animal burrows. (11) Soft areas (12) Livestock damage

(13) Other

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

(2) Excessive grass vegetation that was greater than about 6 feet in height was observed on the downstream slope from approximate Sta. 17+65 to 32+85, which prevented visual observation and inspection. See Photo No. 7.

(11) Several piles of soft soils were observed near the downstream slope and downstream toe contact between Stations 12+80 and 17+75 of the Right Embankment. See Photo No. 16.

PHOTOS: Downstream slope shown on Photo Nos. 7, 10 through 16.

SEEPAGE

PROBLEMS NOTED: (1) None (2) Flow adjacent to outlet (3) Saturated embankment areas (4) Seepage area at toe (5) Seepage exists at point source

(6) Seepage exists on embankment (7) Seepage increased/muddy (8) Other

DRAIN OUTFALLS SEEN? yes no N/A (9) Flow increased/muddy (10) Drain dry/obstructed (11) Pipe deteriorated (12) Animal guard (13) Other

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

(8) Seepage was not observed downstream of the Main Embankment (approximate Sta. 2+60 to 5+50) or the Right Embankment (approximate Sta. 12+80 to 17+65). From Station 17+85 to 32+85, the downstream slope and toe were not visible to observe for seepage conditions due to vegetation (see Photo No. 15). It should be noted that only about 1-foot of water was impounded behind the embankments at the time of the inspection.

(8) A drainage ditch was observed near Station 18+40 that extended from the downstream toe sloped to flow downstream of the dam. Due to the excessive vegetation in this area (grass in excess of 6 feet in height preventing access to the dam toe and downstream slope), it was not possible to determine what contributes water to this drainage ditch. The ditch was dry at the time of the inspection. See Photo No. 15.

(8) The soft soil deposits on the downstream slope and toe appear to be from downstream slope surface erosion; however, these could also be the result of seepage and movement of materials. See Photo No. 16.

PHOTOS: Seepage shown on Photo Nos. 15 and 16.

/ LOWER CRYSTAL DAM 18

[Lower Crystal Springs Dam (Lake No. 7), Ash Meadows NWR] Page 3

DISCHARGE STRUCTURE: Combined Service Spillway Outlet Works at Station 4+40

PROBLEMS NOTED: (1) None (2) Inadequate freeboard (3) Erosion; with backcutting (4) Flow obstructed (5) Upstream/downstream structure deteriorated/undermined (6) Cracks; with displacement (7) Restricted by vegetation

(8) Scour protection: missing; sparse; displaced; weathered (9) Other

INTERIOR INSPECTED? yes no N/A (10) Conduit deteriorated or collapsed

(11) Joints displaced (12) Valve leakage (13) Other

CONTROLS (gates/valves/stoplogs) INSPECTED? yes no N/A (14) Controls not operated during inspection (15) Controls inoperable (16) Poor operating access

(17) Other (including configuration of controls at time of inspection)

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

(7) Heavy vegetation made access and observations of the upstream inlet difficult, see Photo Nos. 17 and 18. The excessive vegetation will reduce the discharge capacity of the structure.

(10) Corrosion and rust was observed on the interior of the CMP conduit, particularly near the water level. See Photo No. 20.

(14 & 15) The stoplogs were not operated during the inspection. The excessive vegetation would restrict the operation of the stoplogs. See Photo Nos. 17 and 18.

(17) Stoplogs were installed about 2 feet above the bottom of the CMP intake riser invert (Elevation 2142.0). See Photo No. 18.

PHOTOS: Combined Service Spillway Outlet Works structure is shown on Photo Nos. 11, 17 - 20.

DISCHARGE STRUCTURE: Emergency Spillway at Station 0+00

PROBLEMS NOTED: (1) None (2) Inadequate freeboard (3) Erosion; with backcutting (4) Flow obstructed (5) Upstream/downstream structure deteriorated/undermined (6) Cracks; with displacement (7) Restricted by vegetation

(8) Scour protection: missing; sparse; displaced; weathered (9) Other

INTERIOR INSPECTED? yes no N/A (10) Conduit deteriorated or collapsed

(11) Joints displaced (12) Valve leakage (13) Other

CONTROLS (gates/valves/stoplogs) INSPECTED? yes no N/A (14) Controls not operated during inspection (15) Controls inoperable (16) Poor operating access

(17) Other (including configuration of controls at time of inspection)

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

(8) No scour protection was installed in the emergency spillway channel approach channel, control section, or discharge channel. Intermittent areas of grass vegetation were present. Erosion was not observed. See Photo Nos. 21 - 23.

(17) Based on the LiDAR data, the emergency spillway is only about 0.5-foot lower than the dam crest. As a result, the emergency spillway is rated as “poor” due to inadequate freeboard.

PHOTOS: Emergency spillway shown on Photo Nos. 21 through 23.

MONITORING

EXISITING INSTRUMENTATION FOUND: (1) None (2) Gage rod (3) Seepage weirs/flumes (4) Piezometers (5) Survey monuments (6) Other

MONITORING OF INSTRUMENTATION? yes no N/A

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

(2) The staff gage was located near Sta. 10+00, upstream of the naturally high topographic area. The staff gage in the reservoir extended to a height of about 6.5 feet, with the reading at the time of the inspection being about 2.1 feet (difficult to read due to vegetation). It appears the staff gage extends above the dam crest elevation. The staff gage is not routinely monitored by the Refuge Staff and does not reference the same datum as the pertinent data in the SEED Report.

PHOTOS: The reservoir staff gage is shown on Photo No. 24.

/ LOWER CRYSTAL DAM 19

[Lower Crystal Springs Dam (Lake No. 7), Ash Meadows NWR] Page 4

HAZARD CLASSIFICATION

HAZARD CLASSIFICATION VERIFIED? yes no

CHANGE IN DOWNSTREAM CONDITIONS? yes no

The U.S. Fish and Wildlife Service authorized W. W. Wheeler and Associates, Inc. to perform a hazard classification evaluation which was completed December 2019. The Hazard Classification Evaluation recommended that Lower Crystal Dam be classified as a low hazard-potential dam.

OVERALL CONDITIONS

Based on this Safety Inspection, the overall condition is determined to be:

SATISFACTORY – No existing or potential dam safety deficiencies (P1) are recognized. Safe performance is expected under all anticipated loading conditions, including such events as the spillway design flood (SDF).

FAIR – No existing dam safety deficiencies (P1) are recognized for normal loading conditions. Infrequent hydrologic and/or seismic events would probably result in a dam safety deficiency.

POOR – A potential dam safety deficiency is recognized for unusual loading conditions that may realistically occur during the expected life of the structure. This term may also be used when uncertainties exist as to critical analysis parameters that identify a potential dam safety deficiency, i.e., further investigations and studies are necessary.

UNSATISFACTORY – A dam safety deficiency exists for normal conditions. Immediate remedial action is required.

REASONS: Lower Crystal Dam was in POOR condition due to the excessive vegetation on the upstream slope, dam crest, and downstream slope that prevent access or observation; excessive vegetation upstream and in the intake of the combined service spillway outlet works which will reduce the discharge capacity; and the dam/spillways not being capable of passing the 100-year flood with one-foot of residual freeboard.

/ LOWER CRYSTAL DAM 20

[Lower Crystal Springs Dam (Lake No. 7), Ash Meadows NWR] Page 5

DEFINITIONS

DAM – An artificial barrier, including appurtenant works, constructed for the purpose of storage, control, or diversion of water.

DAM HEIGHT – The vertical distance between the lowest point on the dam crest and the lowest point in the original streambed.

HYDRAULIC HEIGHT – The vertical distance between the maximum design water level and the lowest point in the original streambed.

STRUCTURAL HEIGHT – The vertical distance between the lowest point on the dam crest and the lowest point of the excavated foundation.

MAXIMUM WATER STORAGE ELEVATION – The elevation commensurate with the maximum impounding capacity of the dam, including temporary storage of flood water.

MAXIMUM DESIGN WATER LEVEL – The elevation commensurate with the maximum water surface elevation as a result of safely passing the Inflow Design Flood (IDF).

HAZARD CLASSIFICATION – Hazard Classification is a rating based on the potential loss of life (as defined below) or property damage downstream of a dam caused by failure or misoperation. Hazard Classification is not determined by the existing condition of a dam and its appurtenant structures or the anticipated performance or operation of a dam.

(1) Low – No persons at risk.

(2) Significant – 1 to 6 persons at risk.

(3) High – More then 6 persons at risk.

SIZE CLASSIFICATION – The structural height or the water storage capacity at maximum water storage elevation, whichever yields the larger size classification, is used to determine the size of a dam. Size classification categories are as follows.

(1) Small dams are structures that are less than 40 feet high or that impound less than 1,000 acre-feet of water.

(2) Intermediate dams are structures that are 40 to 100 feet high or that impound 1,000 to 50,000 acre-feet of water.

(3) Large dams are structures that are more than 100 feet high or that impound more than 50,000 acre-feet of water.

INVENTORY DAM – A dam is included in the Service Inventory of Dams and the National Inventory of Dams if it meets any of the following three criteria.

(1) It exceeds 25 feet in height from the natural bed of the stream (or a watercourse) measured at the downstream toe of the dam, or if it is not across a stream channel or watercourse, measured from the lowest elevation of the outside limit of the dam, to the maximum water storage elevation, and has a storage capacity at maximum water storage elevation in excess of 15 acre-feet.

(2) It exceeds an impounding capacity at maximum water storage elevation of 50 acre-feet and a height, measured as in (1) above, of at least 6 feet.

(3) It has a high or significant hazard classification regardless of height or storage capacity.

NON-INVENTORY DAM – Non-inventory dams are defined as follows.

(1) A low hazard dam that does not satisfy the criteria as set forth in the Inventory Dams.

(2) An interior dike or cross dike located within an impoundment or levee.

OBSERVED CONDITIONS – Observed conditions can generally be defined as,

(1) Good – In general, this part of the structure has a good appearance and conditions observed in this area do not appear to threaten the safety of the dam. No existing dam safety deficiencies are recognized for normal loading conditions.

(2) Fair – Although this part of the structure is maintained, minor deficiencies are noted. A potential dam safety deficiency is recognized for unusual loading conditions that may realistically occur during the expected life of the structure.

(3) Poor – Conditions observed in this area appear to threaten the safety of the dam. Conditions observed in this area are unacceptable. A potential dam safety deficiency is clearly recognized for normal loading conditions. Immediate actions to resolve the deficiency are recommended.

OVERALL CONDITIONS – Overall conditions are defined as,

(1) Satisfactory – No existing or potential dam safety deficiencies (P1) are recognized. Safe performance is expected under all anticipated loading conditions, including such events as the spillway design flood (SDF).

(2) Fair – No existing dam safety deficiencies (P1) are recognized for normal loading conditions. Infrequent hydrologic and/or seismic events would probably result in a dam safety deficiency.

(3) Conditionally Poor – A potential dam safety deficiency is recognized for unusual loading conditions that may realistically occur during the expected life of the structure. This term may also be used when uncertainties exist as to critical analysis parameters that identify a potential dam safety deficiency, i.e., further investigations and studies are necessary.

/ LOWER CRYSTAL DAM 21

[Lower Crystal Springs Dam (Lake No. 7), Ash Meadows NWR] Page 6

(4) Poor - A potential dam safety deficiency is clearly recognized for normal loading conditions. Immediate actions to resolve the deficiency are recommended. (Reservoir restrictions may be considered until the problem is fixed.)

(5) Unsatisfactory – A dam safety deficiency exists for normal conditions. Immediate remedial action is required.

PRIORITY RATINGS – Priority ratings are assigned to recommendations as follows,

(1) Emergency Situation – An emergency situation exists when the structure is in danger of imminent failure and action must be taken immediately to alleviate the emergency.

(2) Priority 1 (P1) – A P1 recommendation indicates that the normal condition of the structure is impaired and the safety of the structure is in jeopardy.

(3) Priority 2 (P2) – A P2 recommendation indicates that conditions do not currently appear to threaten the safety of the dam. Continued deterioration and/or unusual loading may threaten the safety of the dam.

/ LOWER CRYSTAL DAM 22

7. INSPECTION AND PROJECT HISTORY

7. Inspection and Project History

Inspection History The following is the history of the SEED inspections and SEED inspection reports for LOWER

CRYSTAL DAM:This is the initial inspection report for LOWER CRYSTAL DAM.

Project History There is very little documented project history available for Lower Crystal Dam. According to the NID data, the dam was constructed by the Nye County Land Company. The property was subsequently purchased by The Nature Conservancy and then acquired by the U.S. Fish and Wildlife Service and established as part of the Ash Meadows National Wildlife refuge in June of 1984 (FWS, 1985).

/ LOWER CRYSTAL DAM 23

A. PHOTOS

1. View looking right from approximate Station 2+60, the Main Embankment left abutment, at the upstream slope (which is mostly obscured and inaccessible due to vegetation) and the dam crest.

2. View looking left from approximate Station 5+50, the Main Embankment right vegetation) and the dam crest.

/ LOWER CRYSTAL DAM A-1

3. View looking right from approximate Station 12+80, the Right Embankment left vegetation).

4. View looking left from approximate Station 17+65, the last accessible location on the Right Embankment, at the upstream slope (which is mostly obscured and inaccessible due to vegetation).

/ LOWER CRYSTAL DAM A-2

5. View looking right from approximate Station 12+80, the Right Embankment left abutment, at the dam crest.

6. View looking left from approximate Station 17+65, the last accessible location on the Right Embankment, at the dam crest.

/ LOWER CRYSTAL DAM A-3

7. View looking right from approximate Station 17+65, the last accessible location on the Right Embankment, at the dam crest. Note the impassible vegetation covering the dam crest, upstream slope, and downstream slope from Station 17+65 to 32+85 that prevented access and inspection of this section of the embankment.

8. View looking right from approximate Station 5+50 at a topographically high area between the Main Embankment and the Right Embankment.

/ LOWER CRYSTAL DAM A-4

9. View looking left from Station 12+80 at the topographically high area (natural berm) between the Main Embankment and the Right Embankment.

10. View looking right from approximate Station 2+60, the Main Embankment left abutment, at the downstream slope.

/ LOWER CRYSTAL DAM A-5

11. View looking left from approximate Station 5+50, the Main Embankment right abutment, at the downstream slope. Note the combined service spillway outlet works discharge pipe and downstream pool.

12. View looking right from approximate Station 12+80, the Right Embankment left abutment, at the downstream slope.

/ LOWER CRYSTAL DAM A-6

13. View looking left from approximate Station 17+65, the last accessible location on the Right Embankment, at the downstream slope.

14. View looking right at the downstream slope near Sta. 18+55. Note that the excessive vegetation prevented access for inspection in this area.

/ LOWER CRYSTAL DAM A-7

15. View looking upstream from Station 18+40 where a ditch extends from the downstream toe that would convey water downstream of the embankment (dry during inspection). Note that the upstream end of the ditch was physically not possible to access due to the tall, thick grass.

16. Typical mound of soft soil at the downstream toe near Station 16+00.

/ LOWER CRYSTAL DAM A-8

17. View looking upstream at the approach channel to the combined service spillway outlet works at Sta. 4+40. Note the heavy vegetation upstream and in the intake riser. Wingwalls comprised of 2-inch by 4-inch wood boards were installed on either side of the intake.

18. View looking down into the inlet intake of the combined service spillway outlet works, a three-foot-diameter half round CMP riser with stoplogs.

/ LOWER CRYSTAL DAM A-9

19. View looking downstream at the outflow of the combined service spillway outlet works and downstream discharge pool.

20. View looking up into the downstream end of the combined service spillway outlet works from the outlet outfall. Note corrosion on the CMP pipe near the water line.

/ LOWER CRYSTAL DAM A-10

21. View looking upstream at the emergency spillway approach channel from the control section.

22. View looking right and downstream at the control section and downstream discharge channel of the emergency spillway channel at Sta. 0+00.

/ LOWER CRYSTAL DAM A-11

23. View looking downstream at the emergency spillway discharge channel from the control section. Discharges from the emergency spillway flow to the pool downstream of the combined service spillway and outlet works structure.

24. View looking upstream near Sta. 10+00 at the staff gage in the reservoir.