CRFQ AGR26-16 - Exhibit B 9-2024-09-27 BC15 Operation and Maintenance Plan.pdf

ASJV Project Number 18pr007

OPERATION AND MAINTENANCE PLAN

Brush Creek Site 15 Dam (WV05511) Mercer County, West Virginia

Prepared for the USDA Natural Resources Conservation Service

January 5, 2024 (revised September 27, 2024)

ASJV Project Number 18pr007

This Page Intentionally Left Blank

NRCS West Virginia Operation and Maintenance Plan – Brush Creek Site 15 Dam

September 27, 2024 Aterra-Schnabel Joint Venture 18proj007 ©2024 All Rights Reserved

OPERATION AND MAINTENANCE PLAN

Brush Creek Site 15 Dam Mercer County, West Virginia

NRCS Number: WV-470

WVDEP Number: WV05511

Owner/Operator: Green Valley-Glenwood Public Service District Address: 2387 Maple Acres Road Princeton, WV 24739

Prepared By: Aterra-Schnabel JV Address: 300 Brookside Avenue Building 18, Suite 160 Ambler, PA 19002

Date: January 5, 2024

Revision Dates:

1st Revision: 02/01/2024

2nd Revision: 09/27/2024

3rd Revision:

Project 18proj007 ©2024 All Rights Reserved

September 27, 2024 Page 1 Aterra-Schnabel Joint Venture

OPERATION AND MAINTENANCE PLAN

Brush Creek Site 15 Dam (WV05511)

TABLE OF CONTENTS

1.0 BACKGROUND

1.1 Purpose

1.2 Site Description

1.2.1 Site Access

1.2.2 Pre-Rehabilitation Site Description

1.2.3 Summary of Rehabilitation

2.0 OPERATION

3.0 MAINTENANCE AND INSPECTION

3.1 EMBANKMENT MAINTENANCE AND INSPECTION

3.1.1 Embankment Erosion

3.1.2 Groins

3.1.3 Riprap

3.1.4 Heave, Sloughing, and Slides

3.1.5 Vegetation Control

3.1.6 Rodent Control

3.1.7 Sinkholes

3.1.8 Seepage

3.1.9 Embankment Drains

3.1.10 Wet or Boggy Areas

3.1.11 Boils

3.1.12 Settlement

3.1.13 Upstream Stability Berm

3.2 PIEZOMETERS

3.2.1 General

3.2.2 Operation

3.2.3 Maintenance Schedule

3.2.4 Maintenance Record Keeping

3.2.5 Maintenance Procedure

3.3 PRINCIPAL SPILLWAY MAINTENANCE AND INSPECTION

3.3.1 General Concrete Maintenance and Inspection

3.3.2 Principal Spillway Riser

3.3.3 Principal Spillway Conduit

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3.3.4 Principal Spillway Pond Drain Slide Gate

3.3.5 Principal Spillway Water Supply Gates

3.3.6 Principal Spillway Trash Racks

3.3.7 Principal Spillway Guard Rails, Safety Ladder, Platforms, and Manhole Frame and Cover

3.3.8 Principal Spillway Impact Basin, Grating, and Anchors

3.4 AUXILIARY SPILLWAY MAINTENANCE AND INSPECTION

3.4.1 Auxiliary Spillway Roller Compacted Concrete Chute

3.4.2 Auxiliary Spillway Drain

3.5 OUTLET CHANNEL

3.6 ACCESS ROADS

3.7 FLOODPOOL

3.8 COMPONENT REPLACEMENT

4.0 SECURITY MEASURES

5.0 SCHEDULE OF ROUTINE TASKS

5.1 Maintenance and Monitoring Schedule

5.2 Responsible Personnel

5.3 Maintenance Program

5.4 Inspection Schedule

5.5 Inspection Program

6.0 RECORDS

7.0 HAZARD CONCERNS

8.0 SIGNATURES:

LIST OF TABLES

Table 1. Proposed Project Elevations (NAVD88, ft) Table 2. Suggested Frequency of Reading and Assessing the Piezometer Readings Table 3. Piezometer Thresholds

APPENDICES

Appendix A: Site Location Map

Appendix B: Site Vicinity Map

Appendix C: Brush Creek Site 15 Dam Inspection Plan

Appendix D: USDA-NRCS Annual Dam Inspection Checklist

Appendix E: Piezometer Field Form and V-Notch Weir Recording Form

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1.0 BACKGROUND

1.1 Purpose

The Brush Creek Site 15 Dam (WV05511) (Site 15 Dam) is a multiple-purpose flood control and municipal water supply dam designed by the by the U.S. Department of Agriculture, Natural Resources Conservation Service (NRCS) formerly called U.S. Department of Agriculture, Soil Conservation Service (SCS). Site 15 Dam was originally constructed in 1967 as part of a series of 10 floodwater retarding dams in the Brush Creek Watershed of Mercer County, West Virginia. Site 15 Dam is a High Hazard Potential, multi-purpose (flood protection and municipal water supply) dam that impounds the North Fork of Brush Creek and serves a drainage area of approximately 1,719 acres (2.7 square miles). The dam is planned to be rehabilitated in 2024 to meet current NRCS and West Virginia Department of Environmental Protection (WVDEP) dam safety criteria.

Current Sponsors of Site 15 Dam include the West Virginia Conservation Agency (WVCA) (governed by the State Conservation Committee), the Mercer County Commission, the Green Valley-Glenwood Public Service District (PSD), and the Southern Conservation District. Operation and maintenance (O&M) of Site 15 Dam is the joint responsibility of the Site 15 Dam Sponsors. The Sponsors are responsible for the operation, maintenance, and any needed repairs by performing the work or arranging for such work in accordance with an O&M agreement described in the following paragraph. The Sponsors maintain easements for lands upstream and below the top of dam, or as required by NRCS policy for O&M of Site 15 Dam.

Aterra-Schnabel Joint Venture (ASJV) has prepared this plan for the NRCS and Sponsors to provide guidance and instruction to project personnel for the proper operation, maintenance, and inspection of the Site 15 Dam. This plan fulfills the requirements for an O&M manual as outlined in NRCS’s National Operation and Maintenance Manual and the WVDEP Division of Water and Waste Management, Dam Safety Section’s Inspection, Maintenance and Operation of Dams in West Virginia (see respective agency web sites for current requirements). This plan supplements the O&M Agreement signed by the NRCS and the Sponsors. This plan may only be revised by mutual consent of all signatory parties.

This plan does not include procedures for operation under emergency conditions. For emergency situations, an Emergency Action Plan has been prepared and made available to project personnel.

Copies of the Emergency Action Plan may be obtained from the PSD and the Southern Conservation District. This plan was prepared in association with the final dam rehabilitation design (also prepared by ASJV) and will be updated at the completion of the rehabilitation construction.

1.2 Site Description

1.2.1 Site Access

The Site 15 Dam is located in Mercer County, West Virginia, approximately 5 miles southwest of Princeton, WV on the North Fork of Brush Creek. The auxiliary spillway and embankment crest can be accessed via Dan Hale Reservoir Road and Gobbler Run Road. The latitude and longitude of the approximate midpoint of the embankment centerline are 37.324679° N and 81.184431° W, respectively. A site location map is provided in Appendix A, and a site vicinity map is provided in Appendix B.

The toe of the embankment can be accessed as follows:

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Exit WV Route 20 (New Hope Road) at Dan Hale Reservoir Road (CR 20/12).

Proceed ½ mile and turn left (south) on Gobbler Run Road (CR 20/13).

Continue approximately 2,000 ft to the dam. The planned access point for the downstream toe of the dam is a temporary access road installed along the tree line located to the north east of the site and originating at Gobbler Run Road. This temporary access road is shown on the Detailed Design Drawings and includes a temporary stream crossing and wetland impacts.

The auxiliary spillway can be accessed as follows:

Exist WV Route 20 (New Hope Road) at Dan Hale Reservoir Road.

Turn onto Gobbler Run Road as described above and follow to the temporary access described above. The temporary access road shown on the Drawings extends along the area downstream of the embankment toe and ASW exit to provide toe drain and ASW access.

1.2.2 Pre-Rehabilitation Site Description

The Site 15 Dam impounds an approximately 75-acre reservoir with a capacity of approximately 1,520 acre-feet at its normal pool elevation (EL) of 2489.5 feet. At normal pool, the depth of water at the upstream toe of the embankment is about 53 feet. The flood storage capacity at the ASW crest is approximately 2,080 acre-feet, and the top of dam storage capacity is approximately 3,080 acre-feet.

The dam is an approximately 690-foot long zoned earthen embankment with a crest width of about 22 feet and a maximum height of about 76 feet measured from the invert of the PSW conduit to the low point on the crest of the dam. The upstream slope of the embankment ranges from about 2H:1V to 2.5H:1V.

The downstream slope is approximately 2.5H:1V. The embankment consists of a low-permeability core and upstream and downstream shells.

A 4-foot wide seepage collection drain system (trench drain) is located approximately 100 feet downstream of the embankment centerline at the maximum section. The As-Built Drawings provided by the NRCS (USDA-SCS, 1967) indicate the filter material is a blend of sand and gravel that extends up to 4 feet below top of rock. The trench drain includes an 8-inch diameter perforated corrugated metal pipe (CMP) that outlets downstream of the PSW outlet.

The existing PSW is a single-stage NRCS D×3D riser with a covered top and a concrete platform extending almost 13 feet above the covered top. The PSW riser is about 70 feet tall and has inside dimensions of 2 feet by 6 feet. The invert of the riser crest is at the normal pool elevation of the reservoir, EL 2489.5 feet. The riser conveys flows from the reservoir through the embankment via an approximately 370-foot-long, 24-inch-diameter reinforced concrete pipe (RCP) that outlets into a reinforced concrete Type VI impact basin. The invert of the PSW outlet is EL 2430.4 feet. The PSW conduit was constructed with a concrete cradle founded on rock and includes reinforced concrete anti-seep collars spaced along the length of the conduit. Reservoir drain releases are controlled using an 18-inch seating head slide gate, designated the Pond Drain Gate on the 1967 As-Built Drawings, located at the base of the riser on the left face. The Pond Drain gate has an invert at EL 2432.1. Two 18-inch seating head slide gates, designated Water Supply Gate I and II, are located on the right riser face with inverts of EL 2473.7 and 2453.7, respectively. There is also a raw water intake structure located on the right reservoir rim.

The ASW is a 125-foot wide vegetated earth channel constructed in the left abutment. The ASW has a 20-foot long (upstream to downstream) control section at EL 2496.3 feet, approximately 10 feet below the

September 27, 2024 Page 5 Aterra-Schnabel Joint Venture minimum top of the dam elevation. Both the approach channel and exit channel of the ASW slope away from the control section at about a 2 percent grade. Auxiliary spillway flows drain into the North Fork of Brush Creek.

1.2.3 Summary of Rehabilitation

Dam rehabilitation construction is scheduled to start in 2024. Upgrades to the dam to meet current NRCS and WVDEP dam safety criteria include:

Relocating the ASW control section to the downstream end of the existing channel, installing an RCC chute spillway system downstream of the new ASW control section, and extending the left and right training dikes;

Constructing a earthfill stability berm on the downstream slope of the embankment;

Constructing a riprap stability berm on the upstream slope of the embankment;

Constructing a new embankment toe drain system, and abandoning the existing toe drain system in- place;

Extending the PSW conduit and reconstructing the impact basin;

Replacement of various metal components on the PSW riser and other miscellaneous repairs.

Table 1 summarizes pertinent site proposed elevations based on the 2016 survey. These elevations will be updated based on the record survey after the rehabilitation is completed.

Table 1. Proposed Project Elevations (NAVD88, ft)

Reservoir Drain Entrance Invert 2432.1

PSW Conduit Entrance Invert 2431.2

PSW Conduit Outlet Invert 2430.4

Water Supply Gate I Invert 2474.5

Water Supply Gate II Invert 2454.5

PSW Riser Crest (Normal Pool) 2489.5

ASW Crest 2496.3

Minimum Top of Dam 2506.3

NRCS classifies the Site 15 Dam as a high hazard potential dam. WVDEP categorizes the Site 15 Dam as a Hazard Category 1 dam (i.e., high hazard potential dam). The hazard classification is based on the potential for loss of life and property damage that could result from dam failure due to the prevalence of population, bridges, roads, and buildings within the downstream breach inundation zone. Both agencies require that the spillways at the Site 15 Dam safely pass the Probable Maximum Flood (PMF) without overtopping the dam, which for this site is 28.6 inches of precipitation within 6 hours (36.9 inches of precipitation within 24 hours).

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2.0 OPERATION

The PSD will continue to operate Site 15 Dam based on its water supply operating plan to meet the water supply needs using the two (2) water supply gates on the PSW riser, and the raw intake located on the right side of the reservoir upstream of the dam. Floodwater retention for downstream flood damage reduction is controlled by the PWS riser crest and ASW crest and neither requires any operation beyond the maintenance and inspection outlined in the following sections.

3.0 MAINTENANCE AND INSPECTION

NRCS and WVDEP require dam owners to maintain the facility and all appurtenant structures in a safe condition so that the facility will not endanger life, health, safety, or property located upstream or downstream of the facility. Routine maintenance is defined as minor maintenance, the performance of which neither affects the normal operation nor results in a modification of the original design and/or specifications, and may include:

Routine vegetation management, e.g., maintaining consistent cover, removal of woody vegetation, etc.;

Rodent management;

Erosion monitoring and repair;

Minor concrete and roller compacted concrete repairs;

Removal of debris at the inlet structure, PSW weir, impact basin, and ASW;

Visual inspections after flood and earthquake events;

Periodic internal inspection of the PSW conduit and drainage pipes;

Periodic underwater inspection of the upstream stability berm;

Piezometer maintenance;

Annual dam safety inspection;

Site security for the structure and the public;

Compliance with all state dam safety regulations; and/or Maintaining structure functionality as intended based on the rehabilitation design.

Checking for any encroachments/violations of easements and land rights.

Routine maintenance will include repairing and/or replacing vandalized components, worn parts and metal components (e.g. trash rack, gate hardware, etc.) to retain their operational capabilities.

WVDEP requires the issuance of a written permit for any repairs or maintenance involving modifications of a dam from its original design and/or specifications, and any repairs or reconstruction involving a substantial portion of the structure.

The majority of the maintenance required for Brush Creek Site 15 Dam consists of regular inspections to avert minor deficiencies from becoming major hazards. The following sections discuss in detail the general procedures and maintenance that should be performed in a timely manner to provide safe, reliable, and efficient operation of the dam. The plan view of the dam shown in Appendix C locates the key features for maintenance inspection. The USDA-NRCS Annual Dam Inspection Checklist is in Appendix D. As Built Drawings are kept at the PSD and NRCS offices.

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3.1 EMBANKMENT MAINTENANCE AND INSPECTION

3.1.1 Embankment Erosion

Embankment erosion can occur for a variety of reasons, including runoff forming erosion gullies on the upstream and downstream slopes, and vehicle rutting/damage. Damage related to vehicles or surface erosion must be repaired on a continual basis. The size of erosion gullies can increase greatly with slight amounts of rainfall. Early detection of erosion channels can greatly facilitate the necessary repairs of refilling, regrading, and revegetation. Minor erosion can be repaired easily. The first consideration is to use new soil that resists erosion or is of similar soil type to the existing embankment. The new soil should not contain vegetation, organic matter, trash, or large rock fragments. In addition, the new soil should be neither too wet nor too dry but should contain enough moisture to promote satisfactory compaction. Prior to placing new soil, the repair area must be prepared by removing all unsuitable material such as loose soil, brush, roots, trash, or large rocks. Finally, the new soil should be placed in thin layers of approximately six inches and tamped until firm. To prevent future erosion, the repaired area must be protected with erosion resistant rock, riprap, topsoil and sturdy vegetation, or other material appropriate to the surrounding area. The crest of the embankment should be observed for low spots and other signs of irregularity (erosion, rutting, settlement, cracks) and brought to the attention of the NRCS Engineer immediately. Low spots ponding water on the dam crest require filling, grading, and revegetation, as specified above.

3.1.2 Groins

The groins should be kept clear of unwanted vegetation growth such as trees, bushes, and high brush.

Overgrowth can obscure the view of the embankment, prevent a thorough inspection, and promote rodent activity. Weeds can discourage the growth of desirable grasses. Some root systems can decay, providing a conduit for water to pass through and potentially lead to a piping failure. Large trees could be uprooted during a storm, and the resulting void left by the root system could lead to breaching of the dam.

The groins should be stable if there is good vegetation. These areas should be inspected for erosion and gullies and any damage related to surface erosion must be repaired. Heavy brush and trees should be cut back a minimum of 25 feet from the limits of the embankment, and the discharge channel kept clear. Light brush should be cut as required. Small brush (less than one year old) may be chemically treated and left in place.

3.1.3 Riprap

Riprap along the upstream dam waterline and ASW entrance can fail due to wave action, weathering cycles (freeze/thaw), locally steep slopes, vandalism, and overgrowth of vegetation. When riprap fails, it makes the area particularly susceptible to erosion. To repair any erosion or displaced riprap along the upstream dam waterline and ASW entrance, place a 4- to 6-inch layer of AASHTO Size No. 3 aggregate over non-woven geotextile, and cover with 12 to 24 inches of American Association of State Highway and Transportation Officials (AASHTO) Class B R-4 (3" - 12") rock riprap, as needed. Keep riprap area free of trees and brush. Individual riprap pieces should be dense, durable, and free of cracks, seams, and other defects conducive to accelerated weathering.

Any debris collecting along the waterline and riprap should be removed along with any woody vegetation in the riprap. Loose debris could become lodged in the PSW inlet structure trash racks and block flow.

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3.1.4 Heave, Sloughing, and Slides

Slides, sloughs, and heaves may be caused by embankment or foundation movement, an increase in seepage or pore pressure, soil weakening due to water infiltration, locally steep slopes, wave action, or an unusual increase in load on the dam (such as an earthquake, high pool level, rapid lowering of pool level, or additional dead weight on the embankment). Surface cracks in the embankment may allow precipitation to enter the dam and increase pore pressure. These conditions can be harmful because they may expose an interior portion of the embankment directly to the elements. These conditions, if significant, should be brought to the attention of the NRCS Engineer immediately, or at the next annual inspection if only minor.

3.1.5 Vegetation Control

All portions of the dam and ASW should be kept clear of unwanted vegetation growth such as trees, bushes, and high brush. Overgrowth can obscure the view of the embankment, prevent a thorough inspection, and promote rodent activity. Weeds can discourage the growth of desirable grasses. Some root systems can decay, providing a conduit for water to pass through and potentially lead to a piping failure. Large trees could be uprooted during a storm, and the resulting void left by the root system could lead to breaching of the dam. Root systems can also cause uplift of concrete slabs or structures. Heavy brush and trees should be cut back a minimum of 25 ft from the limits of the embankment, and the discharge channel kept clear. Light brush should be cut as required.

Typical vegetation control at Brush Creek Site 15 Dam consists of the following:

Removal of brush and weeds in the riprap and on the upstream dam slope, ASW entrance, and impact basin outlet channel. Small brush (less than one year old) may be chemically treated and left in place.

Routine mowing of the embankment, ASW, and abutments (minimum of two times per growing season).

Any re-seeding and mulching shall meet the requirements of West Virginia Erosion and Sediment Control Field Manual, Section IV Revegetation.

3.1.6 Rodent Control

Rodents such as groundhogs, muskrats, and beavers are naturally attracted to reservoirs. Groundhogs or woodchucks usually burrow into the downstream embankment slope, forming tunnels and dens inside the dam above the phreatic surface. These passageways not only decrease the stability of the dam, but could also become conduits during flooding periods, leading to a breach of the dam. Muskrats usually burrow into the upstream embankment slope. Their burrows begin 6 to 18 inches below the water surface and penetrate the embankment on an upward slant. At distances up to 15 ft from the entrance, a dry chamber may be hollowed out above the water level. Once a muskrat den is occupied, a rise in the water level will cause the muskrat to dig farther and higher to excavate a new dry chamber. Damage and potential problems are compounded where upstream-driven burrows meet downstream-driven burrows, forming an interconnected pipe. Beavers often build dens along the upstream embankment slope and into the dam.

They have also been known to block inlet structures and spillways with their own dams. Constant removal of cuttings placed in inlet structures and spillways is necessary.

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If burrows are found, the animals should be removed and the burrows refilled. Burrows can be filled by pumping a slurry mixture of sand (90%) and cement (10%) into the burrow. The burrow entrance should then be covered with well-compacted earth, and the vegetation re-established. All rodent hole and beaver den locations should be recorded on the annual inspection reports.

3.1.7 Sinkholes

Sinkholes can be caused by internal or external erosion of material, or by rodent activity. Sinkholes are harmful in that they expose an interior portion of the embankment to the elements and may indicate an unstable condition. Sinkholes should be reported immediately to the NRCS Engineer and the condition must be monitored with measurements of size of depth until the sinkhole has been repaired. Mere backfilling of sinkholes, without adequate investigation into the underlying cause, often masks a serious problem within the dam.

3.1.8 Seepage

The appearance of seepage on the upstream or downstream slope, groins, abutments, or downstream areas may be cause for concern. A prominent sign of seepage is the appearance of certain types of vegetation such as cattails, reeds, and mosses, or a change in the color of vegetation. Note that the presence of ruts from the mowing equipment can also indicate a similar change in the color of vegetation.

The type and quantity of seepage should be studied. If a seep produces a flowing discharge, the discharge should also be evaluated for turbidity, and the slightest discoloration is cause for concern.

Changes in seepage quantity and turbidity should be brought to the attention of the NRCS Engineer. All seepage locations and rates shall be recorded on the annual inspection reports.

Seepage at times may exit some distance downstream from the dam. In general, the farther seepage exits from the dam, the lower the potential for concern. However, it is important that all areas of seepage related to the dam be monitored for changes.

3.1.9 Embankment Drains

Embankment drain pipes are provided to collect and convey embankment seepage. The collector and outlet pipes for the drains consist of perforated and solid PVC pipes, respectively. Cleanouts for the drains are provided on the left and right sides of the embankment. The drain pipe interiors can also be accessed by removing the animal guard installed at the seepage collection boxes located on either side of the principal spillway impact basin.

As needed and not more than every five years flush the drain pipes with low pressure water from the cleanouts to remove iron-related bacteria accumulation from the drain pipes.

A robotic camera video inspection of both embankment drains should be conducted every ten (10) years to document the condition of the drains, and to identify collapsed, crushed, or clogged sections of pipe;

sedimentation; open joints; leakage; or other issues. Cleaning of the drain system should be performed, as needed, based on the results of the video inspection.

Routine inspection and maintenance should include seepage monitoring. Changes in seepage quantity, discoloration, and turbidity should be brought to the attention of the NRCS Engineer. The anticipated flow rates from drain outlets will fluctuate as the reservoir water level varies, however the flows are expected

September 27, 2024 Page 10 Aterra-Schnabel Joint Venture to be less than 5 gpm at each drain outlet under normal pool conditions. The observed flow should be noted in the inspection reports. The collection boxes contain a v-notch weir and a staff gage for measuring the flows. Seepage collection boxes, baffle, v-notch weir, staff gage, and embankment drain pipe animal guards should be inspected for damage (vandalism and/or deterioration) and repaired or replaced as necessary.

3.1.10 Wet or Boggy Areas

Wet areas with no measurable flow can be caused by a developed seepage path reaching an external surface, or by ponded rainfall or snowmelt on the surface. Wet areas may indicate an unstable condition if the cause is seepage. The observation must be noted and reported immediately if significant. Wet areas should be noted on annual inspections and monitored regularly.

3.1.11 Boils

Boils are caused by seepage exiting under pressure and may indicate a serious danger. Boils typically occur in areas downstream of the dam. Boils generally pipe soil material, and measures must be taken to filter and discharge the seepage in a controlled manner. Identifying the cause of the boil, and a permanent remedy, usually requires the consultation of the NRCS Engineer. The boil location should be recorded on the inspection report and reported immediately.

3.1.12 Settlement

Settlement is the vertical movement of the ground surface due to consolidation of the underlying soils.

Normal settlement decreases over time starting from the time an embankment is constructed. Most of the total settlement, under normal conditions, will occur during or soon after construction. Continued settlement, or an increased rate of settlement sometime after construction, is an indication of an underlying problem. All settlement shall be recorded on the inspection reports. Significant or increased rates of settlement shall be reported to the NRCS Engineer immediately.

3.1.13 Upstream Stability Berm

Periodically perform underwater inspections of the upstream riprap stability berm. Inspect for sloughing and slides as described in Section 3.1.4. Inspect for displaced riprap in the vicinity of the riser structure that may potentially block the Pond Drain Gate. Bathymetric surveys with side scanning should also be periodically performed to monitor for slope movements. If significant movement has occurred, it should be brought to the attention of a licensed professional engineer immediately.

3.2 PIEZOMETERS

3.2.1 General

Instrumentation plays a vital role in monitoring the effectiveness of seepage control measures within the dam and variations in conditions over time. Water pressure varies from headwater level on the upstream side of a dam to tailwater level, ground water level, or atmospheric pressure on the downstream side of a dam. The headwater, tailwater, and varying pressure across the dam produce seepage forces that must be properly accounted for in stability analyses.

September 27, 2024 Page 11 Aterra-Schnabel Joint Venture

When the piezometers are read, the reservoir level should be recorded using the staff gage mounted on the principal spillway riser. Reservoir water levels are expected to vary seasonally and will have influence on piezometer readings accordingly. When reservoir levels are outside normal operating range, especially higher reservoir levels, more frequent monitoring of the piezometers is required. During significant flood events, piezometers should be read daily until the reservoir level begins to drop.

Piezometers are used to measure the water pressure and phreatic surface caused by seepage in relatively pervious portions of embankments and foundations. Such measurements can be critical because of possible piping or other seepage-induced instability conditions, such as the presence of excess hydrostatic uplift pressures. A vibrating wire piezometer (VWP) is high precision instrument, which has been designed to measure pore water pressures. Its advantages are long lead lengths and very fast response time to changes in pore water pressure. The VWP consists of a magnetic, high tensile strength, stretched wire. One end of the wire is anchored while the other end is secured to a diaphragm that deflects in proportion to the applied pressure. The diaphragm is deflected proportionally with a change in pressure that affects the tension in the wire. As soon as there is any change in the pore water pressure, the change in pressure is reflected in the tension in the stretched wire. The high tensile strength wire is plucked by a coil magnet and resonates at a frequency proportional to the tension in the wire The VWP produces a frequency signal that is converted to pressure.

3.2.2 Operation

There are six vibrating wire piezometers installed within open standpipe piezometers at the site.

Piezometers B 51A, GF 1S, and GF 1D are installed on the crest of the dam. Piezometers GF 2S and GF 2D are on the downstream slope, and GF 3 is near the toe of the dam. Piezometer PZ-2 is located near the toe of the dam left of the impact basin. The piezometers will be read manually and will not have dataloggers. Readings should be taken using the portable readout device from the VWP manufacturer.

Ambient temperature and barometric pressure are recorded at the time readings are obtained using the barometric pressure indicator installed at the right end of the embankment crest. The piezometer locations are shown in Appendix C. Appendix E contains a sample record keeping form to record piezometer readings.

Table 2. Suggested Frequency of Reading and Assessing the Piezometer Readings

Using the results of stability analyses, threshold limits are set. If a reading exceeds the threshold value, a subsequent reading is reviewed to confirm the initial reading. If the threshold was exceeded, an NRCS geotechnical engineer should be contacted immediately to evaluate the readings and determine if there is a dam safety concern and whether or not action should be taken. Thresholds for the piezometers are shown in the table below. After the existing piezometers are raised, and the new top of casing is surveyed, the elevation shown in the table can be correlated with a depth.

During re-filling following rehabilitation

Year 1

Years 2+

Weekly Monthly Quarterly or as determined by the engineer

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Table 3. Piezometer Thresholds1

Piezometer Depth Below Existing Top of Casing, ft2 Preliminary Threshold

Elevation, ft3

B-51A 51 2457.5

PZ-1 >0 psi (pressure gauge) Ground Surface

B-651 (will be replaced with PZ-2)

>0 psi (pressure gauge) Ground Surface

GF-1S 50 2460.0

GF-1D 53 2457.0

GF-2S 33 2446.4

GF-2D 32 2447.3

GF-3 4.5 2435.8

Piezometer levels should be recorded more frequently during and immediately following elevated reservoir levels. Should any significant change be observed during normal operating or elevated reservoir conditions, contact a licensed professional engineer to review the data. The recommended thresholds in Table 3 are based on limited data and steady state seepage modeled conditions that are conservative. Since the piezometers are read manually and data loggers are not being employed, there will be a limited amount of data available in the future for evaluating thresholds for the new vibrating wire piezometers. Each time the piezometers are read, the reservoir water level, ambient temperature, and barometric pressure should be recorded (see Appendix E). It is recommended that the flow entering the seepage collection system also be recorded. Piezometer readings, reservoir water levels, and seepage flows should be plotted so that trends can be identified. Based on the results of future monitoring, the monitoring plan may need to be modified accordingly and thresholds established for the new piezometers. Detailed information is contained in the geotechnical appendix of the design report.

3.2.3 Maintenance Schedule

Regular maintenance of the vibrating wire piezometers shall be scheduled and conducted in accordance with the manufacturer’s recommendations.

3.2.4 Maintenance Record Keeping

A service record shall be maintained for each instrument. This plan will be updated at the completion of the rehabilitation work and the information entered in the service record for each instrument shall include the date of service, observations, serial numbers and calibration factor (as applicable), problems encountered, corrective procedure employed, and persons involved.

1 Thresholds will be established after construction when a series of readings have been obtained.

2 Existing top of casing before piezometers are raised. Revise to new depth after the top of casing of the raised piezometers is surveyed.

3 Preliminary threshold elevations shown will be revised after the instruments are installed and baseline elevations are established

September 27, 2024 Page 13 Aterra-Schnabel Joint Venture

3.2.5 Maintenance Procedure

The maintenance procedure for the vibrating wire piezometers shall performed be in accordance with the manufacturer’s recommendations. Recalibration of vibrating wire piezometers and data loggers shall be performed in accordance with the manufacturer’s recommendations.

3.3 PRINCIPAL SPILLWAY MAINTENANCE AND INSPECTION

3.3.1 General Concrete Maintenance and Inspection

All concrete should be inspected for spalling, deterioration, cracking, visible reinforcing, rusting or staining of concrete, misalignment of joints, settlement, undermining, and seepage. In general, it is good practice to repair deterioration as soon as it is detected. Open joints and cracks should be cleared of vegetation and properly sealed. Concrete deterioration can be caused by a variety of conditions such as a poor mix design, inadequate consolidation, reactive aggregates, hydraulic abrasion/erosion, or weathering.

Concrete deterioration should be reported to the NRCS Engineer prior to the commencement of any major concrete repairs.

3.3.2 Principal Spillway Riser

Beyond the General Concrete Maintenance and Inspection in Section 3.3.1, and Trash Rack maintenance in Section 3.3.6, the riser should be observed for any signs of tilting or movement which should be brought to the attention of the NRCS Engineer immediately.

3.3.3 Principal Spillway Conduit

The conduit through a dam is one of its most important features and must be adequately maintained. The PSW not only includes the pipe transporting the water, but also the lower and upper trash rack at the inlet preventing debris from entering and clogging the pipe. Problems detected during inspection of the conduits should be immediately addressed, and subsequently checked to make sure that the repair was effective. Due to the importance of the conduit and the difficulty of properly repairing it, technical assistance from the NRCS Engineer should be obtained.

The interior of the Principal Spillway Conduit should be visually inspected periodically to monitor its condition, particularly at pipe joints. Joint opening measurements should be compared to previous measurements and can be obtained by using a pipe camera with laser measuring capabilities. If unusual pipe movement is observed, more accurate measurements shall be performed following these two methods (confined space entry requirements will apply):

“Feeler Gages” consisting of 1/16-inch thick pieces of steel inserted full depth into each joint with the joint width measurement taken at about the 2-inch depth distance into the joint.

Digital caliper at four positions on the inside surface of the pipe around the circumference: at the 12- (crown), 3-, 6- (invert), and 9-o’clock positions. Note that the outer edges of the concrete pipe joints are tapered, rounded and/or chamfered.

September 27, 2024 Page 14 Aterra-Schnabel Joint Venture

3.3.4 Principal Spillway Pond Drain Slide Gate

The Manufacturer of the replacement gate will provide literature with recommendations for operation and maintenance. The pond drain slide gate should be exercised in accordance with the Manufacturer’s literature. Improper operation could result in damage to the gate. Lubricate the exposed stem and wheel apparatus in accordance with Manufacturer’s literature. Any difficulty or failure in exercising the slide gate should be investigated and repaired in consultation with the Manufacturer. Repair or replace all non-functional hardware such as stem guides, anchors, and anchor bolts as recommended by the Manufacturer. Some gate leakage can be expected. Manufacturer tolerances are typically 0.1 gpm/ft of perimeter seal which means that leakage could be acceptable up to 0.8 gpm. However, this estimate will be updated at the completion of the rehabilitation work with the manufacturer’s product manual on operation and maintenance specifics. Some sediment may be released downstream when the slide gate is exercised. It is highly recommended that the operating handwheel or crank be removed from the pedestal and stored at a readily accessible location.

3.3.5 Principal Spillway Water Supply Gates

The two (2) water supply gates on the PSW riser should be exercised annually and maintained per the manufacturer's operation and maintenance manual. It is highly recommended that the operating handwheels or cranks be removed from the pedestals and stored at a readily accessible secure location during periods of normal structure operation when the gates are not manipulated. Lubricate the exposed stem and wheel apparatus. Any difficulty or failure in exercising the gates should be investigated and repaired. Repair or replace all non-functional hardware such as stem guides, anchors, and anchor bolts.

Some gate leakage can be expected.

Operation of the gate(s) should also be noted. Rough, noisy, or erratic movement could be the first signs of a developing problem. The causes should be investigated and corrected as soon as possible. Extreme care should be taken to not attempt to "over-close" the gate as this will over-stress the stem and cause damage to the gate, stem, and stem guides. Also, do not attempt to "over-open" the gate as the gate frame or body can be damaged. When operating the gate(s), motion and position of stem rising and lowering must be carefully observed to avoid equipment damage. Excessive force should be neither needed or applied to either raise or lower a gate. If there does seem to be undue resistance, the gate(s) should be worked up and down repeatedly in short strokes until the binding ceases or the cause of the problem should be investigated. If a gate does not properly seal when closed, debris may be lodged under or around the gate leaf or frame. Raise the gate at least two to three inches to flush the debris;

then attempt to re-close the gate. This procedure should be repeated until proper sealing is achieved. If at any time, the sluice gate(s) will not close, open, or otherwise malfunction, stop operating the gate and determine the cause of the malfunction. Contact the NRCS Engineer before resuming gate operation.

Do not try to force a malfunctioning gate(s) to open or close; this may damage the gate and/or the lifting mechanism.

3.3.6 Principal Spillway Trash Racks

The trash racks must be inspected for obstructions to the flow over the crest, and obstructions removed if found. Routine removal of debris collected on the track rack will be necessary. The trash racks must be inspected for damage (vandalism and/or deterioration) and repaired or replaced as necessary. The trash racks should be inspected for excessive bending, loose or missing bolts, missing channels, and

September 27, 2024 Page 15 Aterra-Schnabel Joint Venture corrosion. Detached, severely bent or missing channels and missing bolts should be scheduled for replacement. Loose bolts should be scheduled for tightening. Rusted areas should be scheduled for cleaning and painting. Anchor bolts which are loose in the concrete should require the technical assistance of the NRCS Engineer.

3.3.7 Principal Spillway Guard Rails, Safety Ladder, Platforms, and Manhole Frame and Cover

The guard rails, safety ladder fatigue platforms, ladder anchors, staff gauge, and manhole frame and cover must be inspected for damage (vandalism and/or deterioration) and repaired or replaced as necessary. Also, any obstructions/debris collected on the ladder and/or platforms must be removed.

Anchor bolts which are loose in the concrete should require the technical assistance of the NRCS Engineer.

3.3.8 Principal Spillway Impact Basin, Grating, and Anchors

Beyond the General Concrete Maintenance and Inspection in Section 3.3.1, and the Embankment Drain outlets in Section 3.1.9, the impact basin should be cleared of any debris. The outlet channel downstream of the impact basin should be free flowing to prevent water backing up into the impact basin and weir boxes. Any restrictions or blockages should be removed.

The impact basin grating and anchors must be inspected for damage (vandalism and/or deterioration) and repaired or replaced as necessary. Also, any obstructions/debris collected on the grating must be removed. Anchor bolts which are loose in the concrete should require the technical assistance of the NRCS Engineer.

The riprap at the PSW impact basin outlet can fail due to weathering cycles (freeze/thaw), vandalism, and overgrowth of vegetation. When riprap fails, it makes the area particularly susceptible to erosion. To repair any erosion or displaced riprap along the upstream dam waterline and PSW impact basin outlet, place a 4- to 6-inch layer of AASHTO Size No. 3 aggregate over non-woven geotextile, and cover with 12 to 24 inches of American Association of State Highway and Transportation Officials (AASHTO) Class B R-4 (3" - 12") rock riprap (NCSA ), as needed. Keep riprap area free of trees, brush, and debris accumulation. Care shall be taken to avoid displacement of the riprap during the removal of sediment and debris. Individual riprap pieces should be dense, durable, and free of cracks, seams, and other defects conducive to accelerated weathering..

3.4 AUXILIARY SPILLWAY MAINTENANCE AND INSPECTION

3.4.1 Auxiliary Spillway Roller Compacted Concrete Chute

The ASW is a critical component for the stability and integrity of the Site 15 Dam. The ASW surface from the reservoir to the Roller Compacted Concrete (RCC) chute is vegetated. The ASW control section is the top of the RCC chute and has a concrete starter wall at the upstream end and a stilling basin and concrete cutoff wall at the downstream end. Cracked (exceeding 0.1 inch in width and/or 0.1 inch in depth) or broken/chipped steps shall be repaired. Deterioration of the RCC surface is a concern and should be brought to the attention of the NRCS Engineer. Inspect ASW system after any channel flow.

Investigate (by visual means and/or probing) after significant flow to ensure that the RCC has remained in stable and free of obstructions. If RCC materials show excessive wear or deterioration it should be brought to the attention of the NRCS Engineer to assess the condition and to develop an appropriate

September 27, 2024 Page 16 Aterra-Schnabel Joint Venture repair plan. All repairs should be performed in accordance with Chapter VII of the USBR Concrete Manual or as recommended by the NRCS Engineer.

Inspect the transitions at both the upstream and downstream ends of the RCC chute. Maintain the transitions to match the surface of the vegetated natural ground and remove any debris.

Do not allow woody plants, trees, or shrubs to grow within the ASW system. The performance of the ASW system is heavily dependent on unobstructed channel and can be affected by even small woody growth.

Small brush (less than one year old) may be chemically treated and left in place. If brushy or woody growth has occurred, carefully remove the growth immediately taking care to not disturb the subgrade.

Lack of vegetation and/or deterioration of the RCC should be brought to the attention of the NRCS Engineer.

3.4.2 Auxiliary Spillway Drain

There are 8-inch diameter PVC collector drain pipes under the RCC floor. These drains are designed to relieve uplift pressures which would only occur when there is flow in the ASW. The drains should be inspected annually and after any flow in the ASW and cleaned and repaired as necessary, including animal guards.

3.5 OUTLET CHANNEL

The outlet channel from the PSW impact basin to downstream of the ASW should be free of obstructions.

Fallen trees, debris, dense woody vegetation, and sediment bars can obstruct stream flows and impact the performance of the PSW. Work in the stream channel may require regulatory approval.

3.6 ACCESS ROADS

For a dam to be operated and maintained there must be a safe means of access at all times. The auxiliary spillway and embankment crest can be accessed via Gobbler Run Road, and the toe of the embankment can be accessed via the open area along the tree line located downstream and right of the embankment. Observations for any obstructions/restrictions to access the dam should be made routinely and any required actions needed to service the dam under any weather condition should be made.

3.7 FLOODPOOL

The flood pool, including the sediment pool, shall be free of obstructions. Fallen trees, debris, dense woody vegetation, sediment deposits, and slides can obstruct and/or impact stream flows and the performance of the dam and spillways.

3.8 COMPONENT REPLACEMENT

The following table shows components that may need to be replaced during the dam’s 100 year evaluated life span. The table showcases an anticipated life span of each component and breaks down the cost in 2024 dollars. It should be noted that cost will escalate for future value.

September 27, 2024 Page 17 Aterra-Schnabel Joint Venture

Item Dam Component Anticipated

Lifespan 2024 Item

Cost Quantity

2024 Cost per replacement

Number of replacements in evaluated life

2024 cost for replacement during evaluated life

1 Riser - Handrailing 50 $20,000 1 $20,000 1 $20,000

Riser - Ladder & Fatigue Platform

50 $20,000 1 $20,000 1 $20,000

3 Riser - Staff Gauge 50 $3,000 1 $3,000 1 $3,000

Riser – Trash Racks

50 $50,000 1 $50,000 1 $50,000

5 Riser – Drain Gate 50 $120,000 1 $120,000 1 $120,000

Riser – Water Supply Gates

50 $100,000 2 $200,000 1 $200,000

Impact Basin – Grating

50 $5,000 1 $5,000 1 $5,000

Impact Basin – Guard Railing

50 $20,000 1 $20,000 1 $20,000

Seepage Collection Box – Grating

50 $1,500 2 $3,000 1 $3,000

Seepage Collection Box – Weir

50 $750 2 $1,500 1 $1,500

Seepage Collection Box – Staff Gauge

50 $200 2 $400 1 $400

12 Animal Guards 25 $100 9 $900 3 $2,700

Vibrating Wire Piezometers

25 $500 8 $4,000 3 $12,000

Portable Readout Devices

25 $1,600 1 $1,600 3 $4,800

Barometric Pressure Indicators

25 $2,000 1 $2,000 3 $6,000

September 27, 2024 Page 18 Aterra-Schnabel Joint Venture

4.0 SECURITY MEASURES

Vehicle access to the dam is limited by the PSD and the WVCA. The access gates and locks should be inspected and repaired or replaced as necessary.

5.0 SCHEDULE OF ROUTINE TASKS

5.1 Maintenance and Monitoring Schedule

The recommended schedule of routine tasks for all NRCS dams is outlined in NRCS’s National Operation and Maintenance Plan, and the recommended schedule of routine tasks for all dams in WVDEP Division of Water and Waste Management, Dam Safety Section’s Inspection, Maintenance and Operation of Dams, Rules (47CSR34-16.1.b.), and summarized below:

Weekly:

Monitor and record the reservoir water surface elevation.

Monthly:

Monitor seepage from the drain outlet pipes.

Visually monitor the dam.

Routine maintenance as required.

The recommended frequency for reading the piezometers is shown in Table 2.

5.2 Responsible Personnel

Annual Dam Inspections: Professional Engineer licensed in West Virginia, TBD Maintenance: TBD Coordination of Routine Tasks: TBD

5.3 Maintenance Program

A program has been established whereby routine maintenance is performed at predetermined regular intervals for specific items and equipment, and on an as-needed basis for other areas.

As with inspection reports, records are kept of all maintenance activities. The data includes the date and time the maintenance was performed. Maintenance records include activities such as cleaning, clearing debris from the spillway, tree removal, repairing erosion, etc. Records are kept at the SCD office.

5.4 Inspection Schedule

The inspection schedule for all NRCS dams is outlined in NRCS’s National Operation and Maintenance Manual, and the inspection schedule for all dams in West Virginia is outlined in WV Code Chapter 22, Article 14, Dam Control and Safety Act, and summarized below:

Monitoring: Routine monitoring to observe operation and assess performance. On-site monitoring may be performed by anyone, including landowners, operators, O&M personnel, and NRCS personnel.