B08_140FGA24R0008_Att_20_Dam_Safety_Report.pdf

UPPER PAHRANAGAT DAM (NV10125)

Pahranagat National Wildlife Refuge

Inspection Date: 11/16/2018

TABLE OF CONTENTS

CHAPTER Page

1. Current Conclusions 1

2. Current Recommendations and Cost Summary 4

3. Status of Previous Recommendations 8

4. Screening Level Risk Assessment 12

5. Pertinent Data 14

6. Inspection Checklist 22

7. Inspection and Project History 29

APPENDICES

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

1. CURRENT CONCLUSIONS

A.

B.

C.

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.

Upper Pahranagat Dam was considered to be in POOR condition due to the inadequate capacity of the service spillway/outlet works and emergency spillway to pass the inflow design flood without overtopping the embankment, the presence of large trees located along the upstream slope and downstream toe of the embankment, the presence of trees located in the emergency spillway approach and discharge channels, and the potential seepage on the downstream slope.

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 77.

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

- The dam overtops as a result of routing the 100-year flood.

-The dam is located in an active seismic area and a liquefaction evaluation has not been performed.

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

NV10125 / UPPER PAHRANAGAT DAM 1

D.

A Hazard Classification Evaluation Report for Upper Pahranagat Dam was prepared by Gannett

Fleming in January 2013 which concluded that the dam met the criteria of a low hazard dam. In this evaluation, a two-dimensional model was used to assess the complex flow conditions that exist downstream of Upper Pahranagat Dam. During a sunny day dam failure, the report indicated that

Highway 93 would be overtopped in two locations with a maximum overtopping depth of 0.7-foot and structures within the Refuge Headquarters could be inundated by depths of about 0.3-foot. These downstream impacts were within the "Low Danger Zone" in accordance with the ACER TM No. 11, Downstream Hazard Classification Guidelines, 1988 criteria. The report also indicated that the incremental damage resulting from a breach of Upper Pahranagat Dam during incipient flooding conditions was judged to be minor.

Upper Pahranagat Dam was previously classified as a high hazard potential structure based on a

Hazard Classification Evaluation by W. W. Wheeler and Associates, Inc. dated March 2009 that used a one-dimensional model to estimate the depth of flow over Highway 93.

The U.S. Fish and Wildlife Service created a panel to review the 2013 Hazard Classification

Evaluation by Gannett Fleming. The panel determined that Upper Pahranagat Dam should be classified as a low hazard dam in June of 2014. The Nevada Division of Water Resources reviewed the 2013 Hazard Classification Evaluation by Gannett Fleming and re-classified Upper Pahranagat

Dam to a low hazard structure in March 2017.

During the 2018 SEED inspection, the downstream area was reviewed for any changes in the area downstream of the dam that may affect the hazard classification that were not considered in the 2013

Hazard Classification Evaluation by Gannett Fleming. No changes in the area downstream of the dam were observed. As a result, Upper Pahranagat Dam is properly classified as a Low Hazard Dam.

Hydrology and Hydraulics Review Upper Pahranagat Dam is an intermediate sized, Low Hazard Dam which requires the dam to safely pass the 100-year flood. The 100-year flood was developed for the 2,625 square mile drainage basin by W. W. Wheeler and Associates, Inc. in the Hazard Classification Evaluation dated March 2009.

The analysis is still considered valid and consistent with the 2008 FWS dam safety standards (FWS, 2008). The 2009 hydrology inflow design flood was developed using five sub-basins. The 100-year precipitation was developed based on NOAA Atlas 14 for each of the sub-basins with 24-hour depths ranging from 2.78 to 2.21 inches. The peak inflow into Upper Pahranagat Dam was 87,080 cubic feet per second (cfs) with a 72-hour storm volume of 184,403 acre-feet. The reservoir routing of this storm event results in a maximum water surface of Elevation 3364.68 feet, which results in a maximum overtopping depth of 7.2 feet and overtopping duration of about 4.5 days.

Prior to 2014, and in the last SEED Report that was performed in 2011, Upper Pahranagat Dam was classified as a high hazard dam which resulted in the inflow design flood being the probable maximum flood. As a result of the hazard classification changes, the inflow design flood has been revised.

NV10125 / UPPER PAHRANAGAT DAM 2

E.

F.

G.

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 0.4 to 0.8 g at the dam site.

Four borings were drilled at site as part of the 2008 rehabilitation design (URS, 2011). Based on these borings, the lower portion of the embankment and the upper portion of the foundation consist of potentially liquefiable materials (mostly saturated silty sands and sandy silts).

A liquefaction potential evaluation and deformation analysis is recommended as part of the Additional

Studies and Analyses Recommendation 2018-1SA-01.

Geologic and Geotechnical Review Geologic and geotechnical evaluations were completed as part of the 2008 rehabilitation design.

These evaluations consisted of:

1. Geotechnical properties evaluation of the embankment dam and foundation.

2. Filter compatibility evaluation of existing embankment material and new filter material.

3. Allowable bearing capacity evaluation for the bridge abutment.

4. Axial and lateral pile capacity evaluation.

A slope stability analysis of the existing embankment, along with a seepage evaluation, should be included as part of the final designs recommended in Additional Studies and Analyses

Recommendation 2018-1SA-01.

Civil and Structural Review Civil and structural evaluations were completed as part of the 2008 rehabilitation design. These evaluations consisted of:

1. Structural evaluation of the service spillway/outlet works structure.

2. Structural evaluation of the H-piles used for the service spillway/outlet works structure foundation.

3. Structural evaluation of the service spillway/outlet works downstream concrete headwall.

4. Structural evaluation of the pedestrian bridge abutment.

5. Structural evaluation of the trashracks and gratings.

The existing civil and structural evaluations appear to be in general conformance with current standards and no additional civil or structural evaluations appear warranted at this time.

NV10125 / UPPER PAHRANAGAT DAM 3

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 None

P1 Maintenance Recommendations 0 P1 Maintenance Costs $0.00

Priority 2 Recommendation(s) Cost None

P2 Maintenance Recommendations 0 P2 Maintenance Costs $0.00

Total Maintenance Costs $0.00

Priority 1 Recommendation(s) Cost None

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

Priority 2 Recommendation(s) Cost None

P2 Operations and Monitoring Recommendations 0 P2 Operations and Monitoring Costs $0.00

Total Operations and Monitoring Costs $0.00

Priority 1 Recommendation(s) Cost

1. (2008-1CO-01) Remove all trees, tree stumps, brush, dead brush piles, and dead trees from the upstream and downstream slopes of the dam, the upstream and downstream shoulders of the crest, within 20 feet of the downstream toe, and from within the limits of the approach and discharge channels of the emergency spillway. This recommendation also includes the work involved to repair the embankment after the tree removal, which will include placement of embankment fill, riprap, bedding, and basecoarse. This activity should be coordinated with the RDSO to determine appropriate engineering supervision requirements.

$998,854.74

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E. Additional Studies or Analyses

F. Future Inspections

2. (2008-1CO-02) Regrade supplemental service spillway discharge channel to drain into the emergency spillway discharge channel and locate and uncover the downstream side of the pipes that have been covered with sediment. Additionally, remove trees, brush, and debris from the discharge channel of the supplemental service spillway. This activity should be coordinated with the RDSO to determine appropriate engineering supervision requirements.

$25,579.62

3. (2011-1CO-01) Construct spillway modifications or overtopping design recommended under Additional Studies Recommendation "2018-1SA-01", to safely pass the inflow design flood.

All construction activities associated with this recommendation shall be coordinated with the Regional Dam Safety Officer (RDSO).

$7,610,241.60

P1 Construction Recommendations 3 P1 Construction Costs $8,634,676.00

Priority 2 Recommendation(s) Cost None

P2 Construction Recommendations 0 P2 Construction Costs $0.00

Total Construction Costs $8,634,676.00

Priority 1 Recommendation(s) Cost

1. (2018-1SA-01) Develop Title 1 / Pre-design engineering plans to design dam and spillway improvements to safely pass the 100-year inflow design flood (IDF) with adequate freeboard consistent with U.S. Fish and Wildlife Service dam safety policy. The engineering should also include a liquefaction and deformation analysis of the embankment and a seepage/stability evaluation.

$84,240.00

P1 Additional Studies or Analyses Recommendations 1 P1 Additional Studies or Analyses Costs $84,240.00

Priority 2 Recommendation(s) Cost

1. (2018-2SA-01) The Refuge should coordinate the work on the reconstruction of the Upper Pahranagat Dam Cross Dike with the Regional Dam Safety Officer. The Refuge should confirm that the elevation of the crest of the Cross Dike is lower than the crest elevation of Upper Pahranagat Dam.

$0.00

P2 Additional Studies or Analyses Recommendations 1 P2 Additional Studies or Analyses Costs $0.00

Total Additional Studies or Analyses Costs $84,240.00

Recommendation(s) Cost

1. (2018-1FI-01) Verify if Middle Dike Trail, Whin Dike Trail, or Lower Lake Dike Trail meet the qualifications of an inventory dam per the U.S. FWS criteria.

$2,592.00

Total Future Inspections Recommendations 1 Total Future Inspections Costs $2,592.00

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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 Emergency Recommendations 0 Total Emergency Costs $0.00

Total P1 Recommendations 4 Total P1 Costs $8,718,916.00

Total P2 Recommendations 1 Total P2 Costs $0.00

Total Future Inspection Recommendations 1 Total Future Inspection Costs $2,592.00

Total Recommendations 6 Total Costs $8,721,508.00

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Table 4-1 Operations Schedule

Upper Pahranagat 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 E(1)

Transmit Log & Forms

Flood Operations E E

Instrumentation Reservoir Staff Gage E,A

Piezometers E,B

Drain Outfalls E,C

Survey Points E,D

Inspection Station Inspection (2) E,F

SEED Inspection (3) E

Special Inspection (4) E,F

Conduit Inspection (5)

Maintenance Maintain Gate & Operator

(5) Per Manufacturer’s Recommendation E

Maintain Stoplogs & Hoist

(6) Per Manufacturer’s Recommendation E

Control Vegetation (7) E

General Maintenance E

Fill Rodent Holes E Unusual or Emergency Event Emergency Action E

Shading indicates responsible entity.

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

A Form 2a D Form 2d B Form 2b E Form 1a - Operations Log C Form 2c F 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. The Refuge should particularly monitor the downstream slope and toe for signs of seepage including changes in seepage conditions and signs of movement of embankment materials, particularly from about Station 9+00 to 16+00. If changes in seepage are observed, the Regional Dam Safety Officer should be contacted. Refuge should also monitor vegetation growth and animal burrows.

(3) Alternate Formal SEED Inspection and Intermediate SEED Inspection every 6 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 following large precipitation events and after seismic events.

(5) The outlet conduit was replaced in 2010 and should be inspected about every 10 years. The outlet gate should be operated annually.

(6) Upper Pahranagat Dam does not have the ability to pass the inflow design flood. Removing the stoplogs will result in increased spillway capacity for a limited range of reservoir levels since the discharges are controlled by the outlet conduit capacity at higher reservoir levels.

(7) At least twice during growing seasons.

3. STATUS OF PREVIOUS

RECOMMENDATIONS

1.

2.

3.

4.

C.

1.

3. Status of Previous Recommendations

Year of Estimate: 2011

Emergency Situation

None

Maintenance

PRIORITY 1 Recommendation(s)

None

PRIORITY 2 Recommendation(s) Recommendation (2008-2MA-03): Fill and compact animal burrows on the downstream slope between about Station 8+00 and Station 8+50 and any other locations where animal burrows are observed.

Total Cost:$1,874.27 Response: This recommendation has not been renewed. This is an on-going activity that is addressed in the Operations Schedule.

Recommendation (2011-2MA-01): Fill low areas on right side of service spillway/outlet works discharge channel. Low areas are located approximately 50 feet and 150 feet downstream of the service spillway/outlet works headwall.

Total Cost:$2,453.28 Response: This recommendation has been completed. The Refuge Manager indicated that one low area on the right side of the discharge channel had been repaired. Significant work had been performed recently to remove vegetation from the discharge channel to increase capacity.

Recommendation (2011-2MA-02): Remove fallen tree from service spillway/outlet works discharge channel.

Total Cost:$1,249.51 Response: This recommendation has been completed.

Recommendation (2011-2MA-03): Revegetate bare areas on the downstream slope that were recently burned during the controlled burn.

Total Cost:$4,034.47 Response: This recommendation has been completed.

Operations and Monitoring

PRIORITY 1 Recommendation(s) Recommendation (2008-1OM-01): Monitor the dam at least quarterly when the pool level is higher then elevation 3352.05 (see the General Appendix for a summary of the seepage history) for seepage conditions and/or piping of dam embankment soil on the downstream slope and toe of dam, particularly the soft area approximately 2 feet to 8 feet above the downstream toe between approximately Station 9+20 and Station 16+00 (as reported in the 2002 SEED inspection report). If

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2.

3.

4.

1.

2.

D.

seepage is observed on the downstream slope, contact the RDSO.

Total Cost:$0.00 Response: This recommendation has not been renewed. This recommendation is addressed in the Operations Schedule.

Recommendation (2011-1OM-01): Based on comments received during the 2011 EAP periodic test, contact the Lincoln County Sheriff's office and obtain radio frequencies used by first responders. Program Refuge radios with first responder radio frequency to aid in communications during emergency events. Purchase new handheld radios if current Refuge radios do not support first responder radio frequency.

Total Cost:$2,500.00 Response: This recommendation has not been renewed. Upper Pahranagat Dam was re-classified as a Low Hazard Dam in 2014 by the U.S. Fish and Wildlife Service and in 2017 by the Nevada Division of Water Resources. As a result, an Emergency Action Plan is no longer required.

Recommendation (2011-1OM-02): Read, record, and transmit instrumentation data according to the frequencies listed in the Standing Operating Procedures (SOP). Obtain new water level indicator to read piezometers.

Total Cost:$500.00 Response: This recommendation has been completed.

Recommendation (2011-1OM-03): Remove or secure hand crank for outlet works slide gate.

Additionally, adjust stop-nut to prevent over-closing of slide gate.

Total Cost:$0.00 Response: This recommendation has been completed.

PRIORITY 2 Recommendation(s) Recommendation (2011-2OM-01): Monitor longitudinal crack on upstream shoulder of dam crest between about Station 9+60 and Station 9+90. If longitudinal crack changes (i.e., longer, wider, deeper, and/or slope movement is observed) contact the RDSO.

Total Cost:$0.00 Response: This recommendation has not been renewed. The longitudinal crack was not observed in the 2018 field inspection.

Recommendation (2011-2OM-02): Based on comments received during the 2011 EAP periodic test, consider stockpiling sand and gravel at the dam. Sand and gravel could potentially be stockpiled right of the emergency spillway and/or near the left abutment (campground area).

Total Cost:$2,418.97 Response: This recommendation has not been renewed. Upper Pahranagat Dam was re-classified as a Low Hazard Dam in 2014 by the U.S. Fish and Wildlife Service and in 2017 by the Nevada Division of Water Resources. Materials for emergency repairs are no longer required by the EAP.

Construction

NV10125 / UPPER PAHRANAGAT DAM 9

1.

3.

E.

1.

PRIORITY 1 Recommendation(s) Recommendation (2008-1CO-01): Remove all trees, tree stumps, brush, dead brush piles, and dead trees from the upstream and downstream slopes of the dam, the upstream and downstream shoulders of the crest, within 20 feet of the downstream toe, and from within the limits of the approach and discharge channels of the emergency spillway.

This recommendation has been changed from "2008-1MA-02" to "2008-1CO-01" because it is a Construction recommendation.

All construction activities associated with this recommendation shall be coordinated with the Regional Dam Safety Officer (RDSO).

Total Cost:$843,493.50 Response: This recommendation has been partially completed and has been renewed.

Recommendation (2008-1CO-02): Regrade supplemental service spillway discharge channel to drain into the emergency spillway discharge channel. Additionally, remove trees, brush, and debris from the discharge channel of the supplemental service spillway.

This recommendation has been changed from "2008-2MA-01" to "2008-1CO-02" because it is a Construction recommendation.

All construction activities associated with this recommendation shall be coordinated with the Regional Dam Safety Officer (RDSO).

Total Cost:$25,133.25 Response: This recommendation has not been completed and has been renewed.

Recommendation (2011-1CO-01): Construct spillway modifications or overtopping design recommended under Additional Studies Recommendation "2008-1SA-01", to safely pass the inflow design flood.

All construction activities associated with this recommendation shall be coordinated with the Regional Dam Safety Officer (RDSO).

Total Cost:$3,288,195.00 Response: This recommendation has not been completed and has been renewed.

Additional Studies or Analyses

PRIORITY 1 Recommendation(s) Recommendation (2008-1SA-01): Update the hydrologic/hydraulic analyses, which may include performing an incremental damage assessment (IDA) to determine the appropriate inflow design flood, and prepare designs to safely pass the inflow design flood, consistent with FWS dam safety policy.

NV10125 / UPPER PAHRANAGAT DAM 10

Total Cost:$250,000.00 Response: This recommendation has been partially completed and has been renewed. The incomplete design work is incorporated in recommendation 2018-1SA-01.

Recommendation (2011-1SA-01): Prepare a SEED Analysis Notebook for Upper Pahranagat Dam.

Total Cost:$18,750.00 Response: This recommendation has not been renewed. Upper Pahranagat Dam was classified as a Low Hazard Dam in 2014 and a SEED Analysis Notebook is no longer required.

Future Inspections

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4. SCREENING LEVEL RISK ASSESSMENT

Dam Name:

NID No.:

Station:

Region:

Hazard Classification:

Dam Type:

Dam Height: feet Maximum Storage: 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: 77

Earthfill

Upper Pahranagat Dam

NV10125

Pahranagat National Wildlife Refuge Low

Li ke lih oo d

Static - Gate Failure

Static - Embankment/Foundation Internal Erosion

Seismic - Liquefaction Hydraulic - Overtopping

Static - Instability

Static - Conduit Internal Erosion Hydraulic - Operations

0 1 2 3 4

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Consequences: Level 0

Level 2

Failure Modes:

Likelihood Consequences Score

High Level 2 5

Very High Level 2 10

Low Level 2 1

Low Level 0 0

Extremely High Level 2 30

N/A N/A 0

Low Level 2 1

Extremely High Level 2 30

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

History of seepage or steady/controlled seepage with no observed piping. No filter.

Uncertain soils. 2010 drawings show a toe drain; however, documentation in the 2011 SEED Report indicate this was not constructed due to budget constraints. Current vegetation growth does not allow regular monitoring.

Under minimal releases associated with a failure of the outlet gate, minor damage is expected to the structure and is only expected to result in damage to FWS property.

Description Reason Static Potential Failure Modes Structure instability (static), resulting in failure of the dam. FS is unknown. No known adverse conditions; performance history indicates adequate slope stability. Upstream slope 1.5H:1V, downstream slope 2.5H:1V. Regular monitoring.

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 or foundation materials. Not designed for EQ loading.

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

No observed piping or seepage along conduit/drain. Modern design / construction.

Outlet conduit was replaced in 2010 with a filter collar design. Regular monitoring and releases through the structure. Filter collar drains are not observed regularly due to high tailwater.

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

Gate was installed in 2010 and operated frequently by Refuge staff. Annual full range testing/operation. Regular preventative maintenance per manufacture's specifications.

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

Dam overtopped by the 100-yr flood.

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), shallow inundation of Refuge Headquarter buildings, Highway 93 overtopped by less than 1-foot resulting in minimal economic damage. These consequences were developed by referencing the Hazard Classification Evaluation by Gannett Fleming, 2013.

Dam instability and/or scour of rock foundation due to overtopping (concrete dam), resulting in breach of the reservoir.

Not Applicable. No concrete sections of dam.

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).

Normal operating pool/stoplogs is maintained with recommended minimum freeboard, which are typically not installed. Modern construction and materials since outlet was replaced in 2010. Regular preventative maintenance per manufacture's specifications. Experienced operators. Service spillway has limited capacity to route the IDF.

Seismic Potential Failure Modes

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5. PERTINENT DATA

5. Pertinent Data General

Dam Section(s)

1. Dam Name *: UPPER PAHRANAGAT DAM

2. NID Number *: NV10125

3. Other Dam Name(s) *:

4. Dam Former Name(s) *: Buckhorn Ranch Dam

5. Dam State *: NV

6. Dam County *: LINCOLN

7. Dam Latitude *: 37.29

8. Dam Longtitude *: -115.12

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

S2&3,T8S,R61E

10. River or Stream Name *: WHITE RIVER

11. Basin: COLORADO RIVER

12. Reservoir Name: UPPER PAHRANAGAT LAKE

13. Year Constructed *: 1937

14. Year and Reason Dam Modified *: 1998H, 2010H

15. Downstream Hazard Potential Classification *: LOW

16. Resource Value: Primary Resource

17. Inventory Status: Inventory

18. Size Classification: INTERMEDIATE

19. SAMMS#: 10005093

20. Confined Space: yes

21. Estimated Economic Losses Downstream: > $5 million

Notes:

Item 14: In 1998 the supplemental service spillway was constructed through the emergency spillway crest. In 2010 the combined outlet works/service spillway was replaced.

Embankment Dam Section 1: UPPER PAHRANAGAT DAM

1. Dam Type *: EARTH

2. Crest Elevation: 3,357.5 Ft.

3. Dam (Crest) Length *: 1,515 Ft.

4. Crest Width: 24 Ft.

5. Dam Height *: 15 Ft.

6. Structural Height *: 15 Ft.

7. Hydraulic Height *: 15 Ft.

8. Upstream Slope: 1 H:1V to 1.5 H:1V

9. Downstream Slope: 2.5 H:1V

10. Core Position *: HOMOGENOUS DAM Type *: HOMOGENOUS DAM Certainty *: ESTIMATED

NV10125 / UPPER PAHRANAGAT DAM 14

C.

D.

Saddle Dike(s)

Discharge Structure(s)

11. Foundation *: SOIL Certainty *: ESTIMATED Karst: no

12. Volume of Dam *: 46,000 CY

Notes:

Note: The Upper Pahranagat Dam Cross Dike is located in the reservoir pool, with a dam crest that has been documented to be about 3356.36 feet (Wheeler, 2009). LiDAR data from the refuge verifies that the cross dike is lower than the Upper Pahranagat Dam.

Items 2 through 9: Values are from the 2008 survey performed by Great West Surveying, Las Vegas, Nevada. The elevations referenced refer to the North American Vertical Datum 1988

(NAVD-88).

Item 5: The dam height is based on the the vertical distance between the lowest point on the dam crest and the lowest point in the original streambed; El. 3357.5 - El. 3342.5 = 15.0 feet.

The lowest point in the original streambed is assumed to be equal to the invert elevation at the discharge end of the service spillway/outlet works conveyance pipe (El. 3342.5).

Item 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; El. 3357.5 - El. 3342.5 = 15.0 feet. The lowest point of the excavated foundation is assumed to be equal to the invert elevation at the discharge end of the service spillway/outlet works conveyance pipe (El.

3342.5).

Item 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. 3357.5 - El. 3342.5 = 15.0 feet.

The lowest point in the original streambed is assumed to be equal to the invert elevation at the discharge end of the service spillway/outlet works conveyance pipe (El. 3342.5). The hydrologic analysis performed by Wheeler in 2009 concluded that the 100-year event would result in dam overtopping, therefore the maximum design water level is assumed to be equal to the dam crest (El. 3357.5).

Item 8: The upstream slope varies between 1H:1V to 1.5H:1V based on the 2008 survey.

Item 12: The volume of the dam was reported to be 46,000 cubic yards in the 1984 Initial SEED inspection report.

There are no saddle dikes currently associated with this structure.

Discharge Structure 1: SERVICE SPILLWAY/OUTLET WORKS

1. Discharge Structure Type: Combined Service Spillway and Outlet

Works

2. Description: CONCRETE DROP INLET WITH

STOPLOGS AND LOW-LEVEL

SLIDE GATE

3. Location: CENTERLINE AT STATION 7+46

4. Approach Channel: RESERVOIR

5. Intake Structure: CONCRETE DROP INLET

a. Crest Elevation: 3,352 Ft.

b. Invert Elevation: 3,342.6 Ft.

NV10125 / UPPER PAHRANAGAT DAM 15

c. Size: 8 feet wide x 8 feet long x 15.4 feet tall intake tower (outside dimensions)

d. Material: CONCRETE

e. Width: 8 Ft.

6. Control Structure: STOPLOGS AND SLIDE GATE

a. Type *: UNCONTROLLED

b. Min Control Elevation: 3,342.6 Ft.

c. Max Elevation of Gate Opening: 3,344.6 Ft.

d. Max Control Elevation: 3,358 Ft.

e. Size: TWO 4-FOOT STOPLOG BAYS AND

ONE 24" BY 24" SLIDE GATE

f. Material: ALUMINUM STOPLOGS AND

STAINLESS STEEL GATE

7. Conveyance Structure: 24" I.D. STEEL PIPE

a. Length: 84.8 Ft.

b. Size: 24" I.D. STEEL PIPE

c. Inlet Invert Elevation: 3,342.6 Ft.

d. Outlet Invert Elevation: 3,342.52 Ft.

e. Year of Conduit Installation: 2010

8. Outlet Structure: RIPRAP LINED PLUNGE POOL

a. Energy Dissipation: RIPRAP

9. Discharge Channel: EXCAVATED EARTH CHANNEL

10. Service Spillway Discharge Capacity with Water Surface at *: Top of Dam : 56.4 cfs and is based on the following formula: Q=C*A*(2*g*H)^.5 Outlet Works Discharge Capacity with Water Surface at: Service Spillway Crest : 43.8 cfs and is based on the following formula: Q=C*A*(2*g*H)^.5

Notes:

Items 5 through 7: Elevations and dimensions from the 2011 Record Drawings by URS for the Upper Pahranagat Dam Outlet Works Rehabilitation.

Item 5e: Two stoplog bays, each 4 feet wide.

Item 6d, 6f: From Construction Report for Upper Pahranagat Dam Modifications, July 20, 2011: The stoplogs are aluminum and placed to a maximum elevation equal to the top of the intake structure at elevation 3,358.0 feet.

Item 10 (Service Spillway): For water surface elevations less than 3353.5 feet, the discharge is controlled by the weir and the discharge capacity of the service spillway can be estimated using the following formula; Q=C*L*H^1.5, where H = water surface elevation - service spillway crest elevation (3352 feet), C = 3.0, and L = 8 feet. For water surface elevations greater than 3353.5 feet, the discharge is controlled by the outlet conduit (orifice flow) and the discharge capacity of the service spillway can be estimated using the following formula;

Q=C*A*(2*g*H)^.5, where H = water surface elevation - outlet pipe centerline elevation, C = 0.6, g = gravity, and A = pipe area. It should be noted that the discharge coefficient is dependent on the tailwater elevation and 0.6 is an average value. At the dam crest (EL 3357.5), discharge = 0.6 x 3.14 sq. ft. x (2 x 32.2 ft/s^2 x (3357.5 - 3343.6))^0.5 = 56.4 cfs

Item 10 (Outlet Works): The discharge capacity of the outlet works can be estimated using

NV10125 / UPPER PAHRANAGAT DAM 16

the following formula; Q=C*A*(2*g*H)^.5, where H = water surface elevation - outlet pipe centerline elevation, C = 0.6, g = gravity, and A = pipe area. It should be noted that the discharge coefficient is dependent on the tailwater elevation and 0.6 is an average value. At the spillway crest (EL 3352.0), discharge = 0.6 x 3.14 sq. ft. x (2 x 32.2 ft/s^2 x (3352.0 - 3343.6))^0.5 = 43.8 cfs.

Discharge Structure 2: SUPPLEMENTAL SERVICE SPILLWAY

1. Discharge Structure Type: Service Spillway

2. Description: TWO 18" DIAMETER STEEL PIPES, STOPLOG CONTROLLED

3. Location: APPROXIMATELY STATION 17+25

4. Approach Channel: EMERGENCY SPILLWAY

APPROACH CHANNEL

5. Intake Structure: NA

a. Crest Elevation: 3,352.4 Ft.

b. Invert Elevation: Ft.

c. Size:

d. Material:

e. Width: Ft.

6. Control Structure: STOPLOGS

a. Type *: UNCONTROLLED

b. Min Control Elevation: 3,352.4 Ft.

c. Max Elevation of Gate Opening: Ft.

d. Max Control Elevation: 3,353.9 Ft.

e. Size: 3 FEET WIDE

f. Material: WOOD STOPLOGS

7. Conveyance Structure: TWO 18" STEEL PIPES

a. Length: 45 Ft.

b. Size: TWO 18-INCH-DIAMETER

c. Inlet Invert Elevation: 3,352.4 Ft.

d. Outlet Invert Elevation: 3,351.4 Ft.

e. Year of Conduit Installation: 1998

8. Outlet Structure: NONE

a. Energy Dissipation: NONE

9. Discharge Channel: NATURAL EARTH CHANNEL

10. Discharge Capacity with Water Surface at *: Top of Dam : 35.5 cfs and is based on the following formula: Q=2*C*A*(2*g*H)^0.5 (2 pipes)

Notes:

Item 6b: The minimum control elevation of the supplemental service spillway pipes is at elevation 3352.4 feet with all the stoplogs removed. Elevations from the 2011 Record Drawings by URS.

Item 6e: Stoplog slots span the entrance of both 18-inch-diameter pipes for a total width of about 3 feet.

Item 6d: The stoplogs can vary between the inlet invert of the pipes (elevation 3352.4 feet, all stoplogs removed) and the crown of the pipes (elevation 3353.9 feet, stoplogs installed up to

NV10125 / UPPER PAHRANAGAT DAM 17

the crown of the pipes).

Item 10: The discharge capacity of the supplemental service spillway pipes can be estimated using the following formula; Q=2*C*A*(2*g*H)^.5, where H = water surface elevation -outlet pipes centerline elevation, C = 0.6, g = gravity, and A = pipe area for one pipe. It should be noted that the discharge coefficient is dependent on the tailwater elevation and 0.6 is an average value. At the dam crest (EL 3357.5), discharge = 2 x 0.6 x 1.77 sq. ft. x (2 x

32.2 ft/s^2 x (3357.5 - 3353.15))^0.5 = 35.5 cfs.

Discharge Structure 3: EMERGENCY SPILLWAY

1. Discharge Structure Type: Emergency Spillway

2. Description: EARTH CUT CHANNEL

3. Location: APPROX. CENTERLINE STATION

17+50

4. Approach Channel: NATURAL EARTH

5. Intake Structure: BROAD-CRESTED WEIR

a. Crest Elevation: 3,355.6 Ft.

b. Invert Elevation: Ft.

c. Size:

d. Material: EARTH

e. Width: 115 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.

e. Size:

f. Material:

7. Conveyance Structure: NATURAL EARTH CHANNEL

a. Length: 75 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: NATURAL EARTH CHANNEL

10. Discharge Capacity with Water Surface at *: Top of Dam : 813.2 cfs and is based on the following formula: Q=C*L*H^1.5

Notes:

Item 5a: Elevation from the 2011 Record Drawings by URS.

Item 7a: The discharge channel length was estimated to be approximately 75 feet extending from the control to approximately the location of the channel intersection with the downstream marsh area.

Item 10: The discharge capacity of the emergency spillway can be estimated using the

NV10125 / UPPER PAHRANAGAT DAM 18

E. Reservoir / Flood Hydrology following formula; Q=C*L*H^1.5, where H = water surface elevation - spillway crest elevation, C = 2.7, L=115 feet. At the dam crest (EL 3357.5), discharge = 2.7*115*(3357.5 - 3355.6)^1.5 = 813.2 cfs.

Reservoir Storage Level Elevation (feet) Surface Area

(acres) Capacity (acre-feet)

Maximum Normal Pool * 3,352 404 2,169.5 Discharge Structure 1:

SERVICE

SPILLWAY/OUTLET

WORKS

3,352 404 2,169.5

Discharge Structure 2:

SUPPLEMENTAL SERVICE

SPILLWAY

3,352.4 411 2,325

Discharge Structure 3:

EMERGENCY SPILLWAY

3,355.6 468 3,725

Top of Dam * 3,357.5 484 4,688

Flood Hydrology

1. Inflow design flood: 100-year storm

2. Storm Duration: 24 hours

3. Total Rainfall: 3.21 inches

4. IDF Peak Inflow: 87,080 cfs

5. Storm Volume: 184,403 acre-feet

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

3,364.68 Ft.

7. IDF Freeboard: 0 Ft.

8. Depth of Overtopping:

7.2 Ft.

9. Duration of Overtopping:

109.25 hours.

10. IDF Peak Outflow: 86,229 cfs

11. Drainage Area: 2,625 square miles

12. Drainage Basin Description *:

PRIMARILY

PASTURE

LANDS WITH

MOUNTAINOUS

AREAS

SURROUNDING

THE VALLEY

Notes:

Item: Storage/Capacity Table: The surface areas and capacities reported in this table include the water stored behind the Upper Pahranagat Cross Dike. Storage information from the 2011 Record Drawings by URS.

Items 1 through 11: Upper Pahranagat Dam was re-classified as a low hazard-potential structure by the U.S. Fish and Wildlife Service in 2014. Values were updated from the 2011 SEED report since these referenced the probable maximum flood, which were based on the dam being a high hazard dam. The inflow design flood (IDF) information was obtained from the most recent hydrologic/hydraulic analyses performed by W.W. Wheeler and Assoc. in the 2009 Hazard Classification Evaluation.

Item 3: Varies from 2.78 to 3.21 inches depending on sub-basin.

Item 6 through 10: Information is based on the reservoir routing results in Wheeler 2009, which use spillway discharge curves that are consistent with the 2011 Record Drawings by

NV10125 / UPPER PAHRANAGAT DAM 19

G.

Management

EAP / SOP

URS. However, the 2011 Record Drawings indicate that the service spillway discharge curves are based on the originally designed 26-inch O.D. HDPE pipe. The 26-inch O.D.

HDPE was not installed; a 24-inch I.D. ECS pipe was installed instead. The difference in the size of discharge pipes will not significantly change the results of the reservoir routing.

1. Owner Name *: US FISH AND WILDLIFE SERVICE

2. Owner Type *: FEDERAL

3. Dam Designer *: UNKNOWN

4. Private Dam on Federal Property *: no

5. Field Station: Pahranagat National Wildlife Refuge

6. Dam Purposes *: FISH AND WILDLIFE POND

7. Field Station Contact Information:

Name: JAMES (ROB) VINSON, REFUGE

MANAGER

Address1: HIGHWAY 93 NORTH, MILEPOST 32 Address2: ALAMO, NV 89001 Phone: (775) 725-3417

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: 84551

10. Region: 8

11. Ecosystem: 06

12. Federal Agency Involvement in Design *:

13. Federal Agency Involvement in Construction *: U.S. Fish and Wildlife Service

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 *: U.S. Fish and Wildlife Service

Notes:

Item 3: Original dam designer is unknown. 2010 modifications designed by URS Group, Inc.

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

Notes:

The hazard classification for Upper Pahranagat Dam was changed from high hazard dam to low hazard dam in 2014 by the U.S. Fish and Wildlife Service and in 2017 by the Nevada Division of Water Resources. As a result, an EAP or SOP is no longer required.

NV10125 / UPPER PAHRANAGAT DAM 20

H.

I.

Inspection Details

Pertinent Data Notes The elevation references are taken from the 2008 survey performed by Great West Surveying, Las

Vegas, NV. The elevations referenced refer to the North American Vertical Datum 1988 (NAVD-88).

* denotes data submitted to the NID.

1. Date of Previous Inspection: 06/14/2011 Inspection Type: Formal

2. Date of Most Recent Inspection *: 11/16/2018 Inspection Type: Formal

3. Inspection Frequency *: 5 Est. Date of Next Inspection: 11/16/2024

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:

Internal inspection of the pipes has not been performed since the replacement of the service spillway/outlet works in 2010.

NV10125 / UPPER PAHRANAGAT DAM 21

6. INSPECTION CHECKLIST

Upper Pahranagat Dam, Pahranagat National Wildlife Refuge Page 1

INSPECTION CHECKLIST FOR LOW HAZARD DAMS

DAM NAME: Upper Pahranagat Dam DATE INSPECTED: 11/16/18

NID NO.: NV10125 DATE OF PREVIOUS INSPECTION: 6/14/11

STATION: Pahranagat National Wildlife Refuge WEATHER/TEMP.: Sunny, 60 degrees COUNTY/STATE: Lincoln County, Nevada POOL ELEVATION: 3345.3

HAZARD CLASSIFICATION: LOW TAILWATER ELEVATION: 3344.5

INSPECTED BY: Danielle Hannes, P.E. and Andrea Fasen, E.I.

CHANGE IN INVENTORY STATUS: Inventory Non-inventory No Change

DIRECTIONS: CUSTOMIZE THIS CHECKLIST FOR THE DAM AND APPURTENANT STRUCTURES AS DESCRIBED IN THE PERTINENT DATA SECTION OF THE REPORT. FOR ELEMENTS THAT ARE NOT PRESENT, DELETE THESE SECTIONS. FOR MULTIPLE ELEMENTS (SUCH AS CONCRETE/EMBANKMENT DAM SECTIONS, SADDLE DIKES, AND DISCHARGE STRUCTURES), INSERT NEW SECTIONS

FOR EACH ADDITIONAL ELEMENT.

MARK CONDITIONS FOUND BY CHECKING BOXES AND BOLDING/UNDERLINING WORDS THAT APPLY. GIVE LOCATION AND

EXTENT IN COMMENTS. REFERENCE APPLICABLE PHOTO NUMBERS IN PHOTOS.

UPSTREAM SLOPE – EMBANKMENT – UPPER PAHRANAGAT DAM

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:

Item No. 2 – Trees were observed on the upstream slope that were up to 2-foot in diameter from about Station 1+00 to 3+00.

See Photo No. 1.

Item No. 2 – Shrubs were observed on the upstream slope that prevented observation of portions of the upstream slope near the dam crest from about Station 5+00 to 7+00 and 10+00 to 17+00. See Photo Nos. 2 and 5.

Item No. 2 – Large trees were observed on the upstream slope, particularly between Stations 9+00 and 17+00 with trunks ranging in diameter from about 2-foot to 6-foot. Several large trees have been cut down on the slope; however, the root systems have not been removed. See Photo Nos. 4 and 5.

Item No. 5 – The upstream slope is as steep as 1H:1V in areas just upstream of the dam crest. See Photo No. 3.

Item No. 12 – Large woody debris was observed on the upstream slope near the left abutment. See Photo No. 1.

PHOTOS: See Photo Nos. 1 – 5.

CREST – EMBANKMENT– UPPER PAHRANAGAT DAM

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:

Item No. 7 – Minor vehicle ruts were observed on the dam crest. See Photo No. 9. Ruts were about 6 inches wide and 20 feet long.

Item No. 12 – Longitudinal crack observed during the 2011 inspection from Station 9+60 to 9+90 on the upstream shoulder of the dam crest was not observed during the 2018 inspection.

Item No. 12 – The parking area located left of the left abutment was (and has been) visually observed to be lower than the dam crest. This area in past SEED Inspection reports has been reported to potentially function as an auxiliary spillway. See Photo No. 10.

PHOTOS: See Photo Nos. 6 – 10.

NV10125 / UPPER PAHRANAGAT DAM 22

Upper Pahranagat Dam, Pahranagat National Wildlife Refuge Page 2

DOWNSTREAM SLOPE – EMBANKMENT– UPPER PAHRANAGAT DAM

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 (11) Soft areas (12) Livestock damage

(13) Other

OBSERVED CONDITIONS

GOOD

FAIR

POOR

COMMENTS:

Item No. 2 – Large shrubs made most of the downstream slope and downstream toe impossible to inspect from about Station 2+50 to 17+00. See Photo Nos. 12 - 14.

Item No. 2 – Large trees were observed on the downstream slope, particularly between the left abutment and Station 5+00 with trunks ranging in diameter from about 0.5-foot to 5-foot. See Photo No. 11.

Item No. 3 – Animal burrows were observed on the downstream slope. Typical animal burrows were about 4-inches in diameter and 1-foot deep. See Photo No. 15.

Item No. 10 – Areas of the downstream slope were missing slope protection and soils were observed to be loose in these locations. See Photo No. 16.

Item No. 11 – Soils at the toe were observed to be soft with white mineral deposits from about Station 5+00 to Station 7+00. See Photo No. 17.

PHOTOS: See Photo Nos. 11 - 17.

SEEPAGE – UPPER PAHRANAGAT DAM

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:

Item No. 8 – Seepage was not observed during the inspection; however, the reservoir level was relatively low during the 2018 inspection and the downstream slope and toe were not able to be thoroughly inspected due to excessive vegetation preventing access. Past inspections have documented seepage from about Station 9+20 to 15+50 and the Refuge Manager confirmed that seepage is present at higher reservoir levels.

Item No. 8 – Soils at the toe were observed to be soft with white mineral deposits from about Station 5+00 to Station 7+00, which could be the result of seepage. See Photo No. 17.

Item No. 13 – The filter collar drain pipe outfalls were not observed during the inspection. The tailwater elevation at the time of the inspection was above the elevation documented on the record drawings of the filter collar drain outfalls.

PHOTOS: See Photo No. 17.

NV10125 / UPPER PAHRANAGAT DAM 23

Upper Pahranagat Dam, Pahranagat National Wildlife Refuge Page 3

DISCHARGE STRUCTURE (Combined Service Spillway and Outlet Works) PROBLEMS NOTED: (1) None (2) Inadequate normal 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:

Item No. 13 – The tailwater in the discharge channel submerged the 24-inch-diameter discharge pipe preventing observation of the interior of the pipe. See Photo No. 21.

Item No. 17 – The slide gate was operated during the inspection. The Refuge Manager indicated that the gate is operated frequently. See Photo No. 19 of the gate stem.

Item No. 17 – The Refuge Manager indicated that vegetation was recently removed from the discharge channel. See Photo No.

22.

Item No. 17 – Stoplogs were not installed at the time of the inspection. Slide gate opened to 255 mm (0.84-foot; 42-percent).

PHOTOS: See Photo Nos. 18 - 22.

DISCHARGE STRUCTURE (Supplemental Service Spillway - two steel pipes in the emergency spillway control section) PROBLEMS NOTED: (1) None (2) Inadequate normal 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:

Item No. 4 – The discharge end of the spillway pipes were covered with sediment and not able to be located.

Item No. 5 – The stoplog slots and upstream intake of the pipes were observed to be corroded. See Photo Nos. 24 and 25.

It…