CONDITION ASSESSMENT AND REHABILITATION PLAN

CONDITION ASSESSMENT AND REHABILITATION PLAN Lake Michie and Little River Dams and Pumping Stations

City of Durham Durham, North Carolina

Schnabel Reference 15821003.02

September 2, 2015

City of Durham Condition Assessment and Rehabilitation Plan

CONDITION ASSESSMENT AND REHABILITATION PLAN

TABLE OF CONTENTS

EXECUTIVE SUMMARY .............................................................................................................................. 1

1.0 INTRODUCTION .............................................................................................................................. 6 1.1 City’s Water Supply Reservoirs 1.2 Water Supply Level of Service Requirements

2.0 RAW WATER PUMPING STATION ASSESSMENT .................................................................... 11 2.1 Available Data Review 2.2 Field Condition Assessment of Raw Water Pumping Station Assets 2.3 Summary of Lake Michie Pumping Station Condition Assessment 2.4 Summary of Little River Pumping Station Condition Assessment 2.5 Failure Modes Analysis – Raw Water Pumping Station Assets

3.0 DAM CONDITION ASSESSMENTS ............................................................................................. 22 3.1 Lake Michie Dam 3.2 Little River Dam

4.0 CONSEQUENCE ANALYSIS ........................................................................................................ 31 4.1 Approach 4.2 Pairwise Comparison 4.3 Weighting Consequence Evaluation Criteria 4.4 Pumping Station Results 4.5 Dam Results

5.0 RISK ASSESSMENT ..................................................................................................................... 36 5.1 Risk Assessment Approach 5.2 Risk Assessment Results

6.0 REHABILITATION PLAN .............................................................................................................. 40 6.1 Recommended Rehabilitation Plan Projects 6.2 Prioritizing Capital Improvement and Work Order Projects 6.3 Planning-Level Cost Estimating Approach 6.4 Prioritized List of Capital Improvement and O&M Projects 6.5 Little River Dam Rehab Summary 6.6 Lake Michie Dam Rehab Summary 6.7 Little River Pumping Station Rehab Summary 6.8 Lake Michie Pumping Station Rehab Summary 6.9 50-Year Rehabilitation Plan

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LIST OF FIGURES

Figure ES-1. City of Durham Water Supply System Schematic Figure 1-1. City of Durham Water Supply System Schematic Figure 2-1. Condition and Performance (C&P) Regions Figure 2-2. Total Number of Lake Michie Assets by C&P Region (% of Assets at Each Region) Figure 2-3. Total Number of Assets by C&P Region (% of Assets at Each Region) Figure 3-1. Lake Michie Assets within C&P Regions Figure 3-2. Little River Assets within C&P Regions Figure 5-1. Scatter Graph Distribution of Pumping Station Risk Assessment Scores Figure 5-2. Scatter Graph Distribution of Dams Risk Assessment Scores Figure 6-1. Preliminary Estimate of Expenditures in 10-Year CIP Figure 6-2. Preliminary Estimate of Total Expenditures in 5-Year Increments for 50-Year Plan Figure 6-3. Preliminary Estimate of Durham Dam & Raw Water Pumping Station Capital Improvement

Plan for 10-Year Interval 2016-2025 Figure 6-4. Preliminary Estimate of Durham Dam & Raw Water Pumping Station Capital Improvement

Plan + R&R Projects for 10-Year Interval 2016-2025 Figure 6-5. Preliminary Estimates of City of Durham Long-Range Dam Pumping Station Renewal and

Replacement Expenditures over 50 Year Interval 2016-2065, by Facility

LIST OF TABLES Table 1-1. Durham Water Supply System Elements Table 1-2. Projected Population and Average Day Water Demand (MGD) for Durham Service Area Table 1-3. Existing and Projected Available Supplies for Durham Service Area Table 2-1. Summary of Deficiencies by Asset Class for Lake Michie Pumping Station – Percent in C&P

Region Table 2-2. Summary of Deficiencies by Asset Class for Little River Pumping Station – Percent in C&P

Region Table 3-1. Summary of Deficiences by Asset Class for Lake Michie Dam Assets – Number in C&P

Region Table 3-2. Summary of Lake Michie Dam Stability Analysis Results Table 3-3. Summary of Deficiences by Asset Class for Little River Dam Assets – Number in C&P Region Table 4-1. Pairwise Comparison of Consequence Evaluation Criteria Table 4-2. Pairwise Comparison of Dam/Raw Water Pumping Station Asset Groups Table 4-3. Summary of Consequence Assessment Results Table 6-1. Prioritized Capital Improvement Projects for Pumping Stations Rehabilitation Table 6-2. Prioritized Capital Improvement Projects for Dams Rehabilitation Table 6-3. Lake Michie and Little River Pumping Stations Rehabilitation Plan Capital Improvement

Project Descriptions Table 6-4. Lake Michie and Little River Dams Rehabilitation Plan Capital Improvement Project

Descriptions

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Table 6-5. Types of Recommended Renewal & Replacement Activities, Lake Michie/Little River Raw

Water Pumping Stations Table 6-6. Types of Recommended Renewal & Replacement Activities, Lake Michie/Little River Dams

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APPENDICES

APPENDIX A – LOCATION MAPS FOR LAKE MICHIE DAM AND LITTLE RIVER DAM

APPENDIX B – PUMPING STATION CONDITION ASSESSMENT REPORTS AND FAILURE MODES B.1 Condition Assessment Report for Lake Michie Pumping Station B.2 Condition Assessment Report for Little River Pumping Station B.3 Potential Failure Modes Pumping Stations

APPENDIX C – DAM INSPECTION REPORTS C.1 Lake Michie Dam – 2014 Inspection Report C.2 Lake Michie Dam Underwater Inspection Report C.3 Little River Dam – 2014 Inspection Report C.4 Little River Dam Underwater Inspection Report

APPENDIX D – DAM CONDITION ASSESSMENT FORMS D.1 Lake Michie Dam Condition Assessment Forms D.2 Little River Dam Condition Assessment Forms

APPENDIX E – DAM SAFETY ANALYSES E.1 Lake Michie Dam Stability Analyses E.2 Lake Michie Dam Hydrology and Hydraulics Analyses E.3 Little River Dam Geotechnical Analyses E.4 Little River Dam Hydrology and Hydraulics Analyses

APPENDIX F – POTENTIAL FAILURE MODES ANALYSIS REPORTS F.1 Potential Failure Modes Analysis Report for Lake Michie Dam F.2 Potential Failure Modes Analysis Report for Little River Dam

APPENDIX G – CONSEQUENCE ANALYSIS PAIRWISE COMPARISON TABLES G.1 Consequence Analysis Pairwise Comparison Tables for Pumping Stations G.2 Consequence Analysis Pairwise Comparison Tables for Dams

APPENDIX H – RISK SCORE TABLES H.1 Risk Score Tables for Pumping Stations H.2 Risk Score Tables for Dams

APPENDIX I – REHABILITATION PLAN TABLES FOR PUMPING STATIONS I.1 Pumping Stations Rehabilitation Recommendations, 10-Year Capital Project List Sorted by

Facility and Year I.2 Pumping Stations Rehabilitation Recommendations, 10-Year Capital Project List Sorted by

Year and Risk Score I.3 Proposed Pumping Stations Repair Work Orders I.4 50-Year Prioritized Pumping Stations Rehabilitation Plan (Capital Projects and

Replacement/Rehabilitation), 5-Year Intervals

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APPENDIX J – REHABILITATION PLAN TABLES FOR DAMS

J.1 Dam Rehabilitation Recommendations, 10-Year Capital Project List Sorted by Facility and Year

J.2 Dam Rehabilitation Recommendations, 10-Year Capital Project List Sorted by Year and Risk Score

J.3 Proposed Dam Repair Work Orders J.4 50-Year Prioritized Dam Rehabilitation Plan (Capital Projects and

Replacement/Rehabilitation), 5-Year Intervals

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EXECUTIVE SUMMARY

Introduction

The City of Durham Department of Water Management’s (DWM) goals for the Dam Maintenance and Rehabilitation Project are to (1) provide annual dam safety inspections, Operations and Maintenance Plan updates, and Emergency Action Plan updates; (2) develop a prioritized 50-year plan for rehabilitation of the dams and raw water intake facilities, based on the results of comprehensive condition assessment and criticality analysis of these facilities; and (3) develop enhancements to the preventive maintenance program for the facilities. This Rehabilitation Plan addresses the second project goal.

This Rehabilitation Plan report documents condition and performance assessments performed by the City’s consultants, Schnabel Engineering South, P.C. (Schnabel) and Brown and Caldwell (BC) between February and April 2015. The Plan provides the City with an inventory of dam/raw water pumping station assets, with supporting photographs, condition and performance ratings, lists of observed deficiencies, and recommended projects to address the deficiencies. Schnabel and BC performed a structured risk assessment to prioritize a recommended rehabilitation and replacement program comprised of capital improvement projects and work order projects for the 50-year planning horizon.

Durham’s Water Supply Reservoirs

DWM operates and maintains two raw water supply reservoirs controlled by Little River Dam and Lake Michie Dam, serving over 268,000 customers. Figure ES-1 is a schematic representation of the City’s water supply system.

Figure ES-1. City of Durham Water Supply System Schematic

Lake Michie Dam and its raw water pumping station were constructed between 1924 and 1927. The dam is a composite structure consisting of a concrete gravity section and an earthen embankment section. An uncontrolled ogee spillway is located in the center of the concrete gravity dam and has a crest elevation of 341 ft above mean sea level (MSL), approximately 82-ft above the riverbed. The raw water pumping

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station for the Lake Michie Dam has two electric pumps and two hydro-turbine driven pumps which convey raw water to the City’s water treatment facilities.

Little River Dam and its raw water pumping station was constructed between 1984 and 1987. The dam is a 95-ft high composite structure consisting of a concrete gravity gated spillway section with nine bays, and an earthen embankment section. The spillway controls the normal lake level at 355 ft mean sea level (MSL). The raw water pumping station for the Little River Dam has two electric pumps and one hydro-turbine driven pump which convey raw water to the City’s water treatment facilities.

The Lake Michie/Little River system, with an available supply of 27.9 MGD, is adequate to meet current year demands, but additional water supply facilities will soon be needed as the service area continues to grow. The City is planning to partner with other local area municipalities to develop a regional water supply and treatment facility on Jordan Lake to utilize its allocation there, while continuing to rely on the Lake Michie/Little River system. The full available yield from these facilities, 44.4 MGD, will be required to meet customer needs by the end of the planning horizon in year 2065.

Condition Assessments of Dams and Raw Water Pumping Stations

Schnabel and BC reviewed available data and performed extensive site visits at Lake Michie Dam and Little River Dam during February through April 2015 to observe, document and evaluate the condition and performance of the assets located at these facilities. Schnabel’s evaluations addressed dam and intake assets, while BC’s evaluations addressed raw water pumping station assets. Asset deficiencies related to condition or performance to achieve level of service requirements were identified and prioritized. A dam safety analysis was performed for each dam, investigating hydraulic capacity, dam stability, and geotechnical considerations. The Rehabilitation Plan appendices contain the detailed condition assessment reports for these assessments.

Significant findings of the condition assessments include:

Lake Michie Dam

Dam safety analysis determined that current conditions require a ¾ Probable Maximum Precipitation (PMP) design storm under the NC Dam Safety regulations, and upgrades to the Lake Michie Dam spillway capacity would likely be needed to meet state requirements.

The original reservoir drains are buried under sediment and not functional. State regulatory requirements for a reservoir drain can be met by other existing sluice gates, though mechanical component upgrades would be required.

Deficiencies were observed in the concrete dam drainage and stability analysis. A portion of the right tailrace wall has been undermined. Piezometers in the dam are not functioning properly and should be replaced. Embankment lacks an adequate drainage system.

Lake Michie Pumping Station

Many pumping station components in this 90-year old facility are at (or past) the end of their service lives and require rehabilitation or replacement.

Two electric pumps and one of the hydro-turbine driven pumps are operable. Electric Pump No. 1 has wear-related issues, and Electric Pump No. 2 was out of service during early site visits due


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to a control panel issue; Electric Pump No. 2 has a significantly smaller capacity than Pump No. 1. Hydro-turbine Driven Pump No. 2 has been taken out of service and is used for spare parts for the other hydro-turbine driven pump. Overall, at present the pumping system lacks sufficient reliability and redundancy measures.

Medium voltage electrical equipment and other electrical gear at the pumping station are aged and obsolete and should be replaced.

Several valves and actuators require service life replacements; the hydraulic actuator system is obsolete and maintenance-intensive and should be replaced with electric actuators.

The roofs are in poor condition and should be replaced. The buildings contain lead based paint, as well as some asbestos-containing materials. The buildings’ windows are in poor condition and can no longer be operated. The pump building

humidity is not controlled, which impacts the electrical equipment. The thermal destratification system has not been used for an extended time and replacement of

the system would be required to restore this functionality.

Little River Dam

The left embankment (facing downstream) drainage ditch is significantly eroded and if not addressed, could impact the spillway structure.

The spillway gate actuators, electrical components and controls are not meeting their performance level of service requirements and should be replaced.

Portions of the stop log monorail and guide systems are not well aligned; modifications are needed to ensure reliable operation.

The dam tunnel should be cleaned and a monitoring program should be established. Piezometers are reporting inaccurate water levels. This may be an indication that maintenance

or repairs are needed.

Little River Pumping Station

Many pumping station mechanical and electrical components in this almost 30-year old facility are nearing the end of their service lives, and require rehabilitation or replacement.

Several pumping station assets not in use (e.g., hydro-turbine driven pump, mechanical rake, some electrical/control panels), have a deteriorated condition, and should be demolished and removed if the City does not want to return them to serviceable condition.

Thermal destratification system is not functioning reliably. The electric pumps do not have similar capacities and the facility does not have redundancy to

meet peak day water supply requirements at present or in the future. The pumps are due for repair/overhaul to address normal wear. No backup generator is available to operate the electrical pumps when utility power is unavailable.

Hydraulic actuator system is obsolete and maintenance-intensive, and should be replaced with electric actuators.

The roofs are in poor condition and should be replaced.


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Rehabilitation Plan

Financial requirements of the proposed rehabilitation plan are summarized in Figure ES-2. Recommended projects total approximately $50 million over the 50-year planning horizon. Projects are summarized in the following paragraphs.

Figure ES-2. Preliminary Estimates of City of Durham Long-Range Dam Pumping Station Capital Improvement Projects and Renewal and Replacement Expenditures over 50 Year Interval 2016-

2065, by Facility

Lake Michie Schnabel and BC identified 50 projects to address asset deficiencies in the 10-year CIP and 85 recurring activities within the 50-year planning horizon. At Lake Michie, the Dam Safety issues should be addressed first. The dam does not appear to be in danger of imminent collapse for normal conditions, but Dam Safety issues must be resolved before the dam will be compliant with Dam Safety and considered safe for the more extreme events for which it is required to withstand.

The major Dam Safety issues identified at Lake Michie Dam included the apparent existence of an embankment core wall which was not in the design drawings; need for structural improvements to meet current Dam Safety design storm and spillway capacity needs; need for a subsurface investigation to evaluate embankment soils and foundation conditions; dam stability necessities which require installing post-tensioned anchors, spillway apron deficiencies requiring repair, and rehabbing the sluice gates to address reservoir drainage requirements.

At Lake Michie Pumping Station, a number of wear-related issues and equipment failures demand attention in the near term. The primary condition issues observed are pump wear and redundancy, including one of the two hydroturbine-driven pumps unable to operate; deterioration of the medium


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voltage electrical equipment; obsolete hydraulic actuators for key pump station valves; areas of poor concrete condition; fair/poor roof condition; and lack of ventilation/humidity control in the pump building. Recommended Lake Michie Pumping Station projects include replacement of obsolete electrical equipment, a new standby generator capable of running the electrical pumps, upgraded electric pump capacity to support long-range water demands; and replacing existing hydraulic valve actuators with electric actuators.

Little River Schnabel and BC identified 45 projects to address asset deficiencies in the 10-year CIP and over 100 recurring activities planned within the 50-year planning horizon. The highest risk issues at Little River Dam include the undermined portion of the concrete drainage ditch at the left embankment and the replacing the spillway gate operators. Some of the other large activities recommended in the CIP are rehabbing the diversion tunnel to observe seepage, replacing the deteriorated Fabriform erosion protection, adding an automatic SCADA and security system, and resurfacing the road.

As the Little River Pumping Station nears 30 years in service, many mechanical and electrical assets are nearing the end of their expected service life. Condition issues observed include deterioration of equipment which has not been used (e.g., hydro-turbine driven pump, mechanical rake), thermal destratification system compressor failures, obsolete hydraulic actuators for key pump station valves, areas of poor concrete condition, fair/poor roof condition, and a few areas of deteriorated electrical panels and wiring. Priority was placed on projects to mothball the hydroturbine-driven pump and provide a standby generator capable of running the electrical pumps to enhance pumping redundancy, investigate and correct Raw Water Unit No. 4 pump vibration issues, repair the oil accumulator system and thermal destratification system, and make targeted replacements of deteriorated/obsolete electrical panels.


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1.0 INTRODUCTION

In keeping with the language of the City of Durham’s Strategic Plan, the Department of Water Management (DWM) is tasked with effective stewardship of the City’s physical assets for providing drinking water and wastewater service to the City’s residents. Like many cities, Durham desires to enhance its level of service to utility customers while at the same time controlling operations and capital costs.

The City’s goals for the Dam Maintenance and Rehabilitation Project are to (1) provide annual safety inspections of its dams, Operations and Maintenance Plan updates, and Emergency Action Plan updates; (2) develop a prioritized 50-year plan for rehabilitation of the dams and raw water intake facilities, based on the results of a comprehensive condition assessment and criticality analysis of these facilities; and (3) develop enhancements to the preventive maintenance program for these facilities. This Rehabilitation Plan addresses the second project goal.

The condition and performance (C&P) assessments performed by the City’s consultants, Schnabel Engineering South, P.C. (Schnabel) and Brown and Caldwell (BC), between February and March 2015, which are documented in this Rehabilitation Plan report, provide the City with specific information for each of the dam/raw water pumping station assets evaluated, with supporting photographs, regarding asset inventory, condition and performance ratings, lists of observed deficiencies, and field-based analysis of pump performance. Assets relating to the dam, including intakes, gates and flumes, were assessed by Schnabel Engineering, while assets relating to the raw water pumping stations were assessed by Brown and Caldwell.

Using direct observations and City staff input, Schnabel Engineering and Brown and Caldwell also performed a structured risk assessment for the facilities’ assets, quantifying risk in terms of both likelihood of the failure and the consequences of a failure of an asset to meet level of service targets. Schnabel performed Potential Failure Mode Analyses for the dams to evaluate the most critical dam safety failure modes from a risk perspective. Schnabel also reviewed previous Dam Safety-related analyses and performed preliminary analyses to evaluate compliance with current state Dam Safety criteria. Each of these tools was used to develop a prioritized program of capital improvement projects and work order projects by the City to correct observed deficiencies.

1.1 City’s Water Supply Reservoirs

The Department of Water Management (DWM) operates and maintains two raw water supply reservoirs controlled by Little River Dam and Lake Michie Dam, serving over 268,000 customers. The locations and facilities of these reservoirs are described in Attachment A.

Lake Michie Dam and its raw water pumping station were constructed on the Flat River between 1924 and 1927. The dam is a composite structure consisting of a 550-ft long concrete gravity section and a 390-ft long earthen embankment section. The 300-ft long uncontrolled ogee spillway is located in the center of the concrete gravity dam and has a crest elevation of 341 ft above mean sea level (MSL), approximately 92-ft above the riverbed. The raw water pumping station for the Lake Michie Dam has four pumps and two hydraulic turbines which convey raw water to the City’s water treatment facilities.

Little River Dam and its raw water pumping station was constructed on the Little River between 1984 and 1987. The dam is a 95-ft high composite structure consisting of a 300-ft long concrete gravity gated


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spillway with nine bays, and a 1,200-ft long zoned earthen embankment section. The spillway controls the normal lake level at 355 ft mean sea level (MSL). The raw water pumping station for Little River Dam has two electric pumps and one hydro-turbine driven pump which convey raw water to the City’s water treatment facilities.

is a schematic representation of the City’s water supply system and Table 1-1 summarizes the size and capacities of system elements.

Figure 1-1. City of Durham Water Supply System Schematic


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Table 1-1. Durham Water Supply System Elements

Facility Element Description

Lake Michie

Reservoir

Reservoir Volume - 3.6 billon gallons (surface area 508 acres) Normal Water Surface Elevation - 341 ft MSL Raw Water Intake Flumes – three (3) 42-in, single level Hydroturbine Intake Flumes – two (2) 60-in, single level Reservoir Drains - 72-in main sluiceway, 36-in supplemental sluiceway (both sealed during 1940s)

Pumping Station

2 Motor-Driven Pumps – Horizontal Split Case Type No. 1- 20,820 gpm, 1250 HP, 150 ft Head, 900 rpm No. 2- 13,880 gpm, 500 HP, 103 ft Head, 720 rpm

2 Hydroturbine-Driven Pumps – Horizontal Split Case Type No. 1- 9,000 gpm, 325 HP, 124 ft Head, 900 rpm No. 2- 9,000 gpm, 325 HP, 124 ft Head, 900 rpm

Raw Water Transmission

Two 30-in Raw Water Mains (5,600 ft each) from Pumping Station to former Flat River Pump Station 24-in + 42-in Raw Water Mains (20,700 ft each) to Brown WTP 42-in Raw Water Main Continues from Brown WTP to Williams WTP (additional 32,900 ft)

Little River

Reservoir

Reservoir Volume - 4.9 billon gallons (surface area 550 acres) Normal Water Surface Elevation - 355 ft MSL Tri-Level Intake Tower – three (3) 72-in x 96-in, with reservoir drain (60-in x 60-in) 54-in Gravity Flow Outlet from Intake Tower, invert 343.5 ft MSL – Capacity 32-45 MGD at normal pool, depending on water level in Brown WTP raw water terminal reservoir

Pumping Station

In addition to gravity flow from Intake Tower (above), raw water pumping capabilities: Hydroturbine-Driven Pump – Horizontal Split Case Type

Pump (No. 1) - 20,000 gpm, 680 HP, 120 ft Head, 585 rpm Turbine (No. 2) - 41,000 gpm, 680 HP, 75 ft Head, 595 rpm

2 Motor-Driven Pumps – Vertical Mixed Flow Type No. 3 20,000 gpm, 125 HP, 16 ft Head, 395 rpm No. 4 (2-speed pump) - 20,000/30,000 gpm, 125/350 HP, 16/38 ft Head, 390/585 rpm

Water can be delivered by gravity or motor-driven pumps to Brown WTP, by or Williams WTP by either motor-driven pump or hydroturbine driven pump

Raw Water Transmission

72-in Raw Water Intake to Pumping Station Wetwell (800 ft) 42-in Raw Water Main from Pumping Station to the Intake Structure (1,500 ft) 54-in Raw Water Main from Intake to Brown WTP (10,100 ft)

Brown WTP Terminal Reservoir

Storage Volume 96 million gallons Normal Water Level 348 ft MSL

Williams WTP Terminal Reservoir

Storage Volume 45 million gallons Normal Water Level 394 ft MSL


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1.2 Water Supply Level of Service Requirements

The City’s water supply facilities must provide adequate potable water for Durham residents and businesses, including the Durham County portion of Research Triangle Park (RTP) to meet current and future demands. Even as new water supply facilities are developed, the existing Lake Michie and Little River water supply facilities must be maintained to support the following level of service (LOS) requirements:

Water supply quantities are sufficient for customer consumption, fire protection and system maintenance, including water-quality related distribution system flushing programs.

Water distribution system pressure meets customer commitments. Water quality meets regulatory permit limits at the treatment plants and in the distribution system. Water supply facilities are reliable and not subject to catastrophic failure at any point in the

storage, delivery and treatment system. Redundant equipment and pipelines are provided as needed to support system reliability.

1.2.1 Water Demand Projections

The amount of water supply which is adequate to meet the City’s demands will increase over time as the service area grows. The City of Durham Jordan Lake Allocation Request - Final, dated November 14, 2014, summarizes the forecasted water supply demand through the 2060 planning horizon.

Population forecasts in the Jordan Lake Allocation Request were based on the Durham City/County Planning Department’s analysis of Traffic Analysis Zone (TAZ) data, and assume build-out of Durham’s water supply service area by 2060. The projections estimate an increase in Durham’s service area population from 246,000 in 2010 to over 458,000 by 2060. The projected rates of annual increase in population decline from about 2% per year in 2015 to 1.2% per year by 2060.

Future water demands were estimated in 5-year increments between 2015 and 2060. Residential water demands were based on customer billing records, while non-residential demand projections were based on individual interviews along with customer billing records, incorporating factors like TAZ-projected numbers of employees and a per-employee water use rate within each TAZ. Customer demands for irrigation were accounted separately in the projections. The projections assumed that per-capita usage in all sectors would decrease over time through conservation and water use efficiency technology advances. The City does not yet have a reclaimed water distribution system, and while the City is developing a reuse plan, water supply projections do not currently assume any of the demand will be met by reclaimed water.

Water treatment plant process water is assumed to be 3.4% of the total demand for years 2020 and beyond.

Non-revenue water includes unbilled water use, such as fire protection, line flushing, hydrant testing, construction-related water use, water line leaks or breaks, and street cleaning. This is assumed to by 11.5% of total demand for years 2015 through 2025, 9.5% of total demand for 2030 through 2050, and 7.5% for years 2055 and after.


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Table 1-2 summarizes projected population and average day water demand for the Durham service area from 2010 to 2060, as presented in the 2014 City of Durham Jordan Lake Allocation Request – Final.

Table 1-2. Projected Population and Average Day Water Demand (MGD) for Durham Service Area

Use Sector 2010 2015 2020 2030 2040 2050 2060

Population 246,200 266,300 286,400 329,400 372,400 415,900 458,400

Residential 13.24 14.36 15.47 17.46 19.37 21.19 22.92

Commercial 6.62 6.91 7.19 8.40 9.50 10.53 11.49

Industrial 1.31 1.28 1.24 1.47 1.68 1.89 2.07

Institutional 2.73 2.46 2.19 2.41 2.63 2.84 3.05

WTP Process Water 0.86 0.95 1.04 1.16 1.30 1.42 1.51

Non-Revenue Water 0.51 2.02 3.53 3.24 3.62 3.98 3.33

TOTAL 25.3 28.0 30.7 34.1 38.1 41.9 44.4


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1.2.2 Available Water Supply

Table 1-3 summarizes the City’s average day MGD for current and projected future water supply sources.

Table 1-3. Existing and Projected Available Supplies for Durham Service Area

Source Basin WQ

Classification Available Water Supply (MGD)

Lake Michie Neuse (10-1) WS-III, NSW, CA 27.91 Little River Neuse (10-1) WS-IV, B, NSW,

CA

Existing Jordan Lake Allocation Haw (2-1) WS-IV, B, NSW,

CA 10

Teer Quarry (Emergency Only) Neuse (10-1) WS-IV, NSW Natural Recharge

Only

Requested Additional Jordan Lake Allocation (Nov. 2014)

Haw (2-1) WS-IV, B, NSW, CA 6.5

Notes: 1. Period of Record yield for the Lake Michie/Little River Reservoir system, as determined for memorandum Use of the Teer Quarry Supplemental Raw Water Storage Project (Hazen and Sawyer, 2012)

The Lake Michie/Little River system, with an available supply of 27.9 MGD, is adequate to meet current year demands, but additional water supply facilities will soon be needed as the service area continues to grow.

In November 2014, the City of Durham applied to the North Carolina Department of Environment and Natural Resources (NCDENR) for an additional allocation of 6.5 mgd from Jordan Lake’s water supply pool, as a part of Jordan Lake Water Supply Allocation Round 4. Durham is one of 13 local water supply utilities forming the Jordan Lake Partnership, and together with the others in the partnership, they have been exploring joint development of existing and future water supply allocations via new regional intake and treatment facilities on the western shore of Jordan Lake. At present, and until new shared Jordan Lake intake and treatment facilities are constructed, Durham’s water supply demands are met by water withdrawn from Lake Michie and Little River, which have a combined available supply of 27.9 MGD, as well as other potential short-term water purchases from other utilities.

The City’s plan is to rely on the proposed 16.5 MGD Jordan Lake allocation to “base-load” its daily water supply needs, then utilize the Lake Michie/Little River system when demands are greater than 16.5 MGD. Based on the current demand projections, the Lake Michie/Little River system will be required to meet average day needs throughout the planning horizon, and the full available yield from these facilities will be required to meet customer needs by the end of the planning horizon.

2.0 RAW WATER PUMPING STATION ASSESSMENT

In February-April 2015, Brown and Caldwell staff reviewed available data and performed extensive site visits at the pumping stations for Lake Michie Dam and Little River Dam to observe, document and evaluate the condition and performance of the assets located at these facilities. Asset deficiencies related to condition or performance to achieve level of service requirements were identified and


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prioritized. Appendix B contains the detailed condition assessment reports for the assessments performed at Lake Michie and Little River pumping stations.

2.1 Available Data Review

The following data were made available to the consultant assessment team by DWM staff for review prior to the site visit:

Record drawings of as-built conditions for the dams and raw water pumping stations:

Lake Michie

o 1924 – Flat River Dam Project

o 1949 – Pump Addition Project

o 1963 – 42-in Raw Water Force Main Project

o 1963 – Pump Station Changes Project

o 1983 – 24-in Clear Water Main Project

o 1996 – Flood Erosion Mitigation Project

o 1996 – Parapet Wall Project

Little River

o 1983 – Contract 1 Little River Dam and Reservoir – 54-in Raw Water

o 1984 – Contract 4 Little River Dam and Reservoir – Dam, Pumping Station and Related Facilities

City’s On-Line electronic operations and maintenance (O&M) manual for Lake Michie Dam, including available vendor O&M documentation

Operation and Maintenance Manuals for both facilities (prepared by Hazen and Sawyer, 2012) Pump, motor and generator record data, including pump curves Records of corrective maintenance work orders for 2011-2014

Based on the data review and discussions with City operations and management staff, BC established asset service requirements which were used in evaluating whether assets are capable of meeting the required level of service.

2.2 Field Condition Assessment of Raw Water Pumping Station Assets

Raw water pumping station assets at Lake Michie Dam and Little River Dam were evaluated in terms of their physical condition and operating performance. The assessments were used to determine the likelihood of failure and the consequence of failure (i.e., the components of the risk formula, as discussed further in Section 5.0 Risk Assessment.

Condition Assessment activities were performed as follows:

1) Facilities and assets were photographed to capture the site layout, building elevations and potential issues which have been observed.


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2) Visual assessments were completed for each asset, including asset inventory descriptive information, which will be provided for the NEXGEN AM asset management system.

a) A condition score and performance score was assigned for each asset evaluated, including concrete and steel structures, mechanical equipment, electrical equipment, standby generators, and ancillary systems. The scoring approach is described fully in below.

b) Inspections of each operational pump included comparison of observed pressure readings to published curves to determine actual flow ratings, and vibration testing. Pump flow testing services were performed by subcontractor PP&S. Their test reports are included in each condition assessment report (Appendix B).

c) Inspection of the bridge cranes in April 2015 by the City’s contractor Carolina Hoist & Crane were observed and documented in the condition assessment reports.

d) Structural assessments were performed of the Lake Michie pump house and Little River pump house, including visual assessments of the building, concrete walls and floor, ventilation systems, lighting, windows and weatherproofing. At Lake Michie, in locations where asbestos materials were suspected, material samples were collected and analyzed by subconsultant Matrix Health and Safety to determine lead paint and asbestos content. Inspection reports prepared by Matrix are included in Appendix B.1. Lead paint testing was performed at Lake Michie. Roof condition was not assessed, since DWM had previously decided to replace the roofs at each facility, but the roofs were checked for asbestos content.

Condition assessment forms were completed for each asset inspected, recording descriptive information and asset condition and performance (C&P) ratings.

2.2.1 Condition and Performance Scoring

Condition scores from 1 to 5 were assigned to each evaluated asset during the field assessments performed between February and April 2015. The asset condition scores were assigned as follows:

1. Excellent

2. Slight visible degradation

3. Visible degradation

4. Integrity of component moderately compromised

5. Integrity of component severely compromised

Similarly, Performance scores of 1 to 5 were assigned to each evaluated pumping station or dam asset, based on the following criteria:

1. Component functioning as intended

2. In service, but higher-than-expected O&M requirements

3. In service, but function is impaired

4. In service, but function is highly impaired

5. Component not functioning as intended

Condition and Performance (C&P) rankings are categorized into five regions corresponding with the urgency for rehabilitation, based on graphing the Condition and Performance scores on Figure 2-1.


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Figure 2-1. Condition and Performance (C&P) Regions

The C&P rankings regions are described below:

Region 1 - Good Condition and Performance. The assets with low C&P ranking scores of 1 or 2 are in this category. Recommended action for these types of assets will be “No immediate action required” as no failure is expected for assets categorized in this region.

Region 2 - Moderate Condition and Performance. The assets with at least one moderate condition or performance ranking score of 3 are in this category. Recommended action for these types of assets will be “Initiate More Detailed Inspection” in order to determine the potential risks for failure.

Region 3 - Poor Condition Ranking. The assets with poor condition ranking scores of 4 or 5, but which are performing well (performance ranking scores of 1, 2, or 3) are in this category. Recommended action for these types of assets will be “Schedule Corrective Action Work Order for Near Term”. Although the assets are in service and functioning, issues related to the condition of these assets should be addressed.

Region 4 - Poor Performance Ranking. The assets with poor performance ranking scores of 4 or 5, but with condition ranking scores of 1, 2, or 3 are in this category. Recommended action for these types of assets is “Immediate Corrective Action Required” as the asset is not functioning properly, or failure is imminent.

Region 5 – Poor Condition and Performance. The assets with poor condition and poor performance scores of 4 or 5 are in this category. Recommended action for these types of assets will be “Replace / Refurbish” as the asset is not functioning properly and the integrity of its components are either moderately or severely compromised.

2.3 Summary of Lake Michie Pumping Station Condition Assessment

BC assessed a total of 90 raw water pumping station assets. As illustrated on Figure 2-2 and Table 2-1, 33 percent of the assets ranked were categorized as being in Regions 3, 4 or 5, which are C&P regions where further action may be an urgent priority.


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Performance Ranking

5 4 3 2 1

Cond

ition

Ra

nkin

g

5 Region 5 – 8 (9%) Region 3 – 6 (7%)

4

3 Region 4 – 15 (17%) Region 2 – 27 (30%)

2 Region 1 – 34 (38%)

1

Figure 2-2. Total Number of Lake Michie Assets by C&P Region (% of Assets at Each Region)

Table 2-1. Summary of Deficiencies by Asset Class for Lake Michie Pumping Station – Percent in C&P Region

Asset Class C&P Region 1 C&P Region 2 C&P Region 3 C&P Region 4 C&P Region 5

Bar Screen 1 0 0 0 1

Building 2 5 0 0 0

Civil Assets 5 2 1 1 0

Compressor 2 0 0 0 0

Crane 0 3 0 0 0

Electrical 10 1 4 2 4

Flow Meter 0 1 0 6 0

Instrument 0 0 0 0 0

Mechanical 1 0 0 0 0

Miscellaneous 0 0 0 0 1

Motor 3 3 0 0 0

Pump 2 3 0 0 2

Sluice Gate/Valve 0 0 0 17 0

Valve 14 12 1 4 1

Treatment Process 0 0 0 1 0

The results of the condition assessment for Lake Michie are incorporated into the risk assessment and were used to determine prioritization of recommended Rehabilitation Plan projects.

2.3.1 Pumping Station Civil Assets

The Civil assets and facility grounds were found to be in good condition overall. There appeared to be adequate parking in grassy areas at the site, and the automatic entrance gate, gravel driveway, and chain link fencing and gate were in good condition. Some debris was observed dumped in the woods adjacent to the mile-long entry drive along Flat River, and some masonry blocks were stacked inside the facility


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gate. Two area lights in the parking area, as well as wall-mounted lights outside the roll-up door the elevator pent-house, were in fair condition. Additional outside lighting would be recommended.

No potable water supply is currently available for the site, and there are no working restroom facilities within the pumping station. A portable toilet is provided for workers outside the pumping station roll-up door. Further evaluation is needed to confirm adequate protection is provided for personnel and equipment.

2.3.2 Pumping Station Structural Assets

The roof condition for the pumping station and elevator penthouse is fair/poor, and the roofs appear to be leaking. Replacement of the roofs is recommended and it is our understanding that a capital project is currently planned to address this.

Overall the south wall and west wall are in good condition, but the windows at both the lower and upper levels are in poor condition, and the mechanisms to operate the windows are no longer functioning as designed. As a result, ventilation of this room is impeded. The steel frames on the single-pane windows are showing signs of corrosion, and should be replaced or have extensive repairs. The humidity in this room and lack of ventilation impact the pump building electrical gear. Measures to enhance ventilation of the pump building, or at least the electrical equipment, are recommended.

Significant concrete repairs for holes, spalling and cracking, are recommended at both the pumping station and elevator penthouse. Leaks and delamination were observed in the pump building’s north interior wall, adjacent to the tunnel entrance. Concrete beams and columns in the lower level are in overall good condition. There is minor spalling at a one beam due to poor cover during initial concrete placement.

Southern Elevator Company, the Department’s contractor for elevator inspections, conducted its annual elevator inspection in January 2015, and the inspection results supplement BC’s observations. The elevator is functional, and passed its most-recent annual certification inspection. The elevator at Lake Michie Dam pumping station is one of the state’s oldest elevators still in service. The steel cable used to raise/lower the elevator was replaced in 2013.

Water leaks observed in the dam’s gallery tunnel should be corrected, and drainage in the tunnel should be improved. Further observations relating to the dam gallery are addressed in Section 3.

The pump building structure is in generally good condition, considering its age, though staining and discoloration were observed on exterior surfaces throughout. The building exterior requires a general cleaning. The buttress below the downspouts along south side of the pumping station is deteriorated, and restoration of the entire buttress is recommended.

2.3.3 Lead Paint and Asbestos-Containing Materials

As part of the structural evaluation at Lake Michie raw water pumping station, Matrix Health and Safety performed a limited survey to identify lead-based paints and asbestos-containing materials. This report is included as an attachment to Appendix B.1. Deteriorated lead-based paint was observed in walls, structural columns, piping, window sashes, door casings, dam gate operators, metal floor gratings, stair treads, stringers and handrails. The walls should be repainted, either sealing over the lead-based paint or


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first removing the existing layers of paint. Asbestos-containing materials were found in the office floor tile and mastic, pipe flange gasket material, and parapet wall roof flashing material. The evaluation of lead-based paint and asbestos-containing materials was not exhaustive, and they may also exist in other areas.

2.3.4 Pumping Station Mechanical Assets

2.3.4.1 Pumps and Associated Valves

Based on documentation provided, the current pumps were installed in 1964, though at least the housing for Hydroturbine-Driven Pumps No. 1 and No. 2 hydroturbines date from the original 1924 facility. Lake Michie’s caretaker/operator indicates that at present, normally either Hydro-turbine Pump No. 1 or Electric Pump No. 1 is operated, and Electric Pump No. 2 is operated on weekends. While both electric-driven pumps are Worthington Model 20LN28, and impeller size for both are the same, however, Electric Pump No. 1 has a 50% higher nameplate capacity and higher operating head enabled by higher pump speed and larger motor. The pumping station firm capacity is based on the lower-capacity Electric Pump.

Hydroturbine No. 2 was taken out of service 6 years ago, after a damaged bearing caused shaft deflection, which in turn damaged the shaft packing seal. Hydroturbine No. 2 is now used to provide spare parts for Hydroturbine No. 1. Hydroturbine-Driven Pump No. 2 was taken out of service at the same time, though Department of Water Management (DWM) staff report the pump was functioning before going out of service.

Hydroturbine No. 1 is currently in fair condition and performing its intended function. Hydroturbine-Driven Pump No. 1 is in good condition, though high vibration is suspected on the inboard bearing based on pump noise and vibration observations. The pump has small water leaks from the split case bolts, and the frame and mounting bolts coating is deteriorated and rusted. Repair of these deficiencies is recommended.

Electric-Driven Pump No. 1 is in fair condition. Visual observations indicate a prior overhaul of this pump. The tests performed by subcontractor PP&S, Inc. indicated significant vibration. The coupling should be serviced, coatings on the frame should be replaced, and the pump should be removed from service for cleaning and inspection, including measuring fits and clearances and replacing parts as necessary to return the pump to original pump curve performance. Seal lines are leaking slightly, and the motor has leaks on the bearings.

Electric-Driven Pump No. 2 is in fair condition. Visual observations indicate newer packing has been installed since pump installation in the 1960s. The coupling should be serviced, and coatings on the frame need replacing. Water leaks from the split case bolts and gasket.

Overall, the valves and piping for the pumps were in generally fair condition, though condition issues were noted for several valves.

2.3.4.2 Other Mechanical Assets

Bar rack and mechanical rake systems at Lake Michie are not used. If the mechanical rake is used in the future, the winch system will need to be rehabilitated or replaced.


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The oil accumulator and pump system was in fair/poor condition, but staff report the system is turned off when not in use due to excessive leaks. Compressors are in good condition, though some oil leaks were observed and the reservoir tank may be due for a hydro test.

The thermal destratification system is not currently used.

The pumping station’s bridge crane, hoist and trolley are in generally good condition.

2.3.5 Electrical Assets

Electric power is provided to the dam and pumping station by Duke Energy through a single 24,950V overhead primary feeder, and a pad-mounted transformer outside the pumping station steps the voltage down to 2,400V 3-phase service for the pumping station electrical facilities. The 1,200 amp medium voltage switchgear / motor control center (MCC) assembly distributes power to the two Electric-Driven Pump motors. An additional step-down transformer reduces the voltage to 120/208V 3-phase which is used for the remainder of the power distribution throughout the facility.

Overall, the Lake Michie Facility electrical assets are aged, worn, and deteriorating. The majority of panels, combination motor starters, and boxes at Lake Michie did not appear to be properly grounded / bonded and are not sufficiently labeled. In several instances, conduits are detached from fittings and mounts.

The condition assessment of the medium voltage switchgear / MCC revealed that the switchgear main disconnect cannot be opened safely and properly. Although the main disconnect was thrown in the “open” position, power was still being delivered to the MCC section of the switchgear where the motor controllers for the medium voltage pump motors are located. The switchgear, automatic transfer switch, 2400-120/208V transformer, high voltage contactors and LodTrak Relays were assessed in June 2015 when the City arranged for Duke Energy to shut the main power feed to the site. The medium voltage electrical gear should be replaced.

2.4 Summary of Little River Pumping Station Condition Assessment

BC performed visual condition assessment on a total of 135 facility assets. Assets are categorized in one of the five Condition and Performance (C&P) regions, as defined in Section 2, based on C&P scores assigned during the field assessment. As illustrated on Figure 2-3 and Table 2-2, 17 percent of the assets ranked were categorized as being in Regions 3, 4 or 5, which are C&P regions where further action may be required.


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Performance Ranking

5 4 3 2 1

Cond

ition

Ra

nkin

g

5 Region 5 – 4 (3%) Region 3 – 5 (4%)

4

3 Region 4 – 13 (10%) Region 2 – 12 (9%)

2 Region 1 – 101 (75%)

1

Figure 2-3. Total Number of Assets by C&P Region (% of Assets at Each Region)

Table 2-2. Summary of Deficiencies by Asset Class for Little River Pumping Station – Percent in C&P Region

Asset Class C&P Region 1 C&P Region 2 C&P Region 3 C&P Region 4 C&P Region 5

Actuator 1 0 0 0 0

Bar Screen 1 0 0 0 1

Building 5 1 0 0 0

Civil Assets 8 0 0 1 0

Compressor 1 0 1 1 0

Crane 4 1 0 0 0

Electrical 45 5 2 6 3

Flow Meter 0 0 0 2 0

Generator 0 1 0 0 0

HVAC 2 0 0 0 0

Instrument 1 1 0 0 0

Mechanical 0 0 0 1 0

Miscellaneous 0 1 0 0 0

Motor 2 0 0 1 0

Valves 20 1 0 0 0

Pump 2 2 1 1 0

Safety 1 0 0 0 0

Sluice Gate/Valve 13 0 0 0 0

Treatment Process 0 0 0 0 0

2.4.1 Pumping Station Civil Assets

Civil assets were in good condition overall. There appeared to be adequate parking on asphalt paving outside the pumping station and elsewhere at the site, and the motorized entrance gate, asphalt entry


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driveway and chain link fencing and gate were in good condition. Site drainage around the pumping station is captured at two drop inlets which empty at the river at the tailrace retaining wall. There are four wall-mounted lights, in good condition, outside the pumping station.

No potable water supply is currently available for the dam, pump station or caretaker’s house. Restroom facilities within the pumping station use water from a non-potable well; a septic tank is used for the restroom.

2.4.2 Pumping Station Structural Assets

The roof conditions for the pumping station, intake structure and stop log building are fair/poor, and the roofs appear to be leaking. The roofs should be replaced and it is our understanding that a capital project is currently planned to address this.

Overall, the structures are in good condition. Efflorescence was observed at the top of exposed concrete masonry walls on the main level. Spalling and cracking on exterior concrete was observed at each of the structures, particularly the intake structure and stop log building. Seepage was observed through cracks in the common wall between the lower pump building level and the intake wet well. Exterior cracks should be repaired to prevent further deterioration.

2.4.3 Pumping Station Mechanical Assets

2.4.3.1 Pumps and Associated Valves

At present, either motor-driven pump Raw Water Unit No. 3 or motor-driven pump Raw Water Unit No. 4 is operated; the Hydroturbine-driven pump has not been operated since facility startup although it is not isolated from the system. While both motor-driven pumps are Worthington Model 30MN33, and impeller size for both are the same, Unit No. 4 has a 47% higher nameplate capacity and higher operating head enabled by higher pump speed and larger motor.

Hydroturbine Raw Water Pump Unit No. 1 is currently serviceable but the function is impaired due to failures in shaft packing and drive shaft couplings oil leaks. Raw Water Pump Unit No. 2 (Hydroturbine-Driver for raw water pump unit No. 1) appears in good condition, but is not being used. Since the pump is not used, it should be isolated from the system and placed in a “mothballed” state to preserve the pump for future use.

Single-speed Electric-Driven Raw Water Pump Unit No. 3 is in good condition. This pump is used for an average of one month per year. The packing should be replaced and packing drainage needs to be fixed. When not being used, pumps should be rotated once a month to preserve the pump and motor bearings.

Two-speed Electric-Driven Raw Water Pump Unit No. 4 is in fair condition. The packing should be replaced and the packing drainage needs to be fixed. The coatings have failed excessively because of packing water overflowing and should be replaced. PP&S noted vibration in this pump above recommended limits, possibly due to alignment issues, bearing failing or pumping against a dead head. Vibration analysis with full-spectrum readings is recommended to evaluate the bearing issue.


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The oil pump system is in fair/poor condition. There are multiple leaks and the oil appears to be contaminated, which if left in this condition will damage the pumps and actuators. Repair is recommended, until hydraulic actuators are replaced with electric actuators.

Overall, the valves and piping for the pumps were in generally good condition, though minor condition issues were noted for several valves.

2.4.3.2 Other Mechanical Assets

The bar rack is in good condition. The mechanical rake has not been used in 20 years and is missing a motor. If DWM desires a functioning mechanical rake, the motor must be replaced.

The pumping station’s bridge crane, hoist and trolley are in generally good condition. The ON/OFF switch for the Little River Dam’s stop log crane, hoist and trolley system was stuck on “ON” position.

The service air compressor is out of service, though some oil leaks were observed.

The destratification compressor system has been unreliable and has multiple oil leaks that need to be repaired. Repairs to eliminate leaks and replacement of the compressor are recommended. The interior of the system is covered with oil including the air intake.

2.4.4 Electrical Assets

Electric power is provided to the dam and pumping station by Duke Energy by a buried primary feeder. A pad-mounted transformer is located in the southwest corner outside of the pumping station. The transformer steps the voltage down to 480/277V, 3-phase, 4 wire service for the pumping station electrical facilities. There is a 2000 amp, 480/277V MCC located in the electrical room. The MCC distributes power to the Pump Building, Stop Log Building and Intake Structure. Two (2) 480-120/208V transformers located in the MCC are used to supply voltages for lighting and other 120/208V loads in the Pump Building. A 480/277V emergency generator is located in the Stop Log Building and provides emergency power to critical lighting, gates, and communication loads in the Pump Building and Stop Log Building.

Overall, the electrical assets at the Little River Facilities are in good condition. The majority of panels, enclosures, and boxes at Little River appear to contain equipment grounding conductors. Conduit appears to be in good condition. The MCC enclosure, main breaker, and overcurrent protective devices for the Stop Log Building and Intake Structure appear to be in good condition.

The Lake Level DP Cell was not being utilized and was unplugged from the wall in the Intake Structure.

Emergency power is provided for lighting, control panels, and roller gate operation by a 30 kW, 480V, 3-phase diesel generator, with an electronically-operated ATS. The automatic transfer switch is in good condition.

2.5 Failure Modes Analysis – Raw Water Pumping Station Assets

It is critically important the raw water pumps station assets reliably and effectively provide water to the City’s water treatment facilities, and support the City’s commitments for customer level of service. BC completed a brief structured failure modes analysis (FMA) exercise as part of the condition assessment to


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identify causes of equipment failures and measures which would reduce the likelihood of these failures. The FMA was used in combination with condition assessments to develop rehabilitation project recommendations, and will drive future preventive maintenance plans for dam pumping station assets. The table in Appendix B.3 summarizes the FMA findings.

The FMA identified possible failure causes that would reduce the reliable delivery of raw water; the causes were organized by equipment type. The majority of the identified failures will be addressed by routine preventive maintenance practices, to be developed by BC and City staff in the Preventive Maintenance Program, a future task of this project.

The Risk Assessment is described fully in Section 5.0, but it is noted here that risk is typically defined in terms of the likelihood of an asset failure, and the consequences of that failure. Several pumping station assets present significant risks to the City, because the consequences of the assets’ failure to perform its function are high. The FMA for pumping station assets identified several failure modes which require capital projects to reduce the likelihood of failure on these high-risk assets. The identified failure modes are predominately a single point of failure on antiquated/obsolete equipment. The major projects arising from the FMA are:

Add backup generators at the Lake Michie and Little River pumping stations Add a second electrical transformer with a separation wall for the incoming power feeds at Lake

Michie and Little River Replace the hydraulic valve actuator systems at Lake Michie and Little River with electrical

actuators Rehabilitate or replace one of the Lake Michie hydro-turbine pumps and its driver (City has

elected to address this failure mode through a backup generator)

3.0 DAM CONDITION ASSESSMENTS

The condition assessments for dam assets for Lake Michie Dam and Little River Dam were evaluated using four different approaches:

Visual inspections including underwater inspections - qualitative description of observations and review of instrumentation data.

Condition and performance (C&P) assessment - assets were assigned a C&P score. Dam safety analyses - hydraulic capacity, dam stability, and geotechnical aspects were checked

for compliance with North Carolina dam safety regulatory requirements. Potential Failure Modes Analysis - risk of dam failure was evaluated.

A summary of the findings are described below for Lake Michie Dam and Little River Dam.

3.1 Lake Michie Dam

3.1.1 Visual Inspection

The objective of the inspection task was to observe, document, and evaluate the conditions of both the concrete and embankment sections of the dams, the abutments, spillways, gates, intake and outlet structures, and other appurtenances to identify and prioritize potential dam safety, long-term reliability,


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and/or O&M issues. The inspection at Lake Michie Dam was conducted on February 24-25, 2015, while the spillway was flowing. A subsequent spillway inspection was performed on July 8, 2015 to observe the condition of the concrete on the spillway when the spillway was not flowing.

The inspection included interviews with the operations and maintenance personnel regarding the performance of each dam since the last dam safety inspection, as well as review of recent repairs or maintenance activities, and instrumentation data collected. An on-site visual inspection of the dams and appurtenant structures was performed by Schnabel Engineering staff, accompanied by DWM operations staff familiar with the dam facilities. An inspection report summarized the inspection, observations and findings from the field inspection, including photographs, and evaluation of available instrumentation data. The report identified O&M issues observed and recommendations for follow-up engineering studies and/or dam repairs and is included in Appendix C.

Schnabel and a dive inspection team from Glenn Underwater Services performed an underwater inspection on April 14-15, 2015. The underwater inspection summary is included in Appendix C. The 36-inch and 72-inch diameter waste flumes, which are the original reservoir drains, were submerged below sediment and debris and therefore not visible. All other sluice gates on the upstream face of the dam were observed to be in poor condition and will not operate in the current state. A full replacement of the sluice gates, stem guides, and gates is recommended. Wooden stop logs were installed upstream of the sluice gates and protected the gates against debris and sediment. The stop logs were in poor condition and are in need of replacement. The trash rack was mostly clogged with growth and debris and needs to be water-jetted clean prior to being functional. Routine water-jet cleaning of the trash rack and dredging of the sediment upstream of the gates will be needed to keep the replacement gates and stop logs functional. The concrete on the upstream face of the dam was in fair condition with deterioration typical of a 91-year old dam. The left tailrace wall and draft tube outlet were in fair condition. However, the right tailrace wall showed signs of erosion and heavy undermining and will require repairs to stabilize the wall.

3.1.2 Condition Assessment

Similar to the pumping station assessment (discussed in Section 2.2), dam assets were assigned a condition and performance score based on field observations. Each asset was categorized under an asset group. The following asset groups at Lake Michie Dam were identified:

Embankment Concrete Gravity Dam Spillway Outlet Works Trailrace and Draft Tubes Reservoir Access and Fencing Instrumentation Dam Electrical

Condition assessment forms were completed during the field inspection and the forms are organized by asset group. The forms show the condition and performance scores for each asset and are included in Appendix D. Figure 3-1 shows the distribution of assets for each C&P region.


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Figure 3-1. Lake Michie Assets within C&P Regions

Table 3-1 shows the number of Lake Michie Dam assets within each C&P region.

Table 3-1. Summary of Deficiences by Asset Class for Lake Michie Dam Assets – Number in C&P Region

Asset Class C&P Region 1

C&P Region 2

C&P Region 3

C&P Region 4

C&P Region 5

Michie Embankment 4 2 0 0 1 Michie Concrete Gravity Dam 8 4 0 0 0

Michie Spillway 0 7 0 0 0 Michie Outlet Works 0 1 0 5 1

Michie Tailrace and Draft Tubes 4 1 0 1 0 Michie Reservoir 1 0 0 0 0

Michie Access and Fencing 0 3 0 1 0 Michie Instrumentation 2 0 0 2 1

Michie Electrical 1 1 0 0 0

The majority of the assets were in C&P regions 1 and 2. The outlet works trash rake, gallery piezometers, and embankment drainage system are the three assets in C&P region 5. The outlet works trash rake, while in a poor performance and condition category, is no longer needed for operations.

3

7

2

16

23

0 5 10 15 20 25

C&P Region 5

C&P Region 4

C&P Region 3

C&P Region 2

C&P Region 1

Number of Lake Michie Dam Assets within C&P Regions


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3.1.3 Dam Safety Analyses

Schnabel reviewed available reports and analyses for Lake Michie Dam and in some cases performed preliminary engineering analyses to identify potential dam safety deficiencies related to the NC Dam Safety regulatory requirements. The analyses included hydraulic capacity evaluation, design storm evaluation, reservoir drain viability, and structural stability evaluation, and are summarized in the following sections. An embankment stability analysis was not performed due to the unavailability of data to appropriately conduct an assessment. Technical memorandums summarizing these evaluations are included in Appendix E.

3.1.3.1 Hydrology and Hydraulic Analysis Summary

Based on the size and hazard classification (large and high hazard) for Lake Michie Dam, the NC Dam Safety requires the design storm to be the ¾ Probable Maximum Precipitation (PMP). The Inspection and Dam Safety Assessment report for Lake Michie Dam from November 20, 1996 states that a previous incremental analysis was made which showed that the flood generated by storms larger than ½ PMP does not cause more damage than the flood from a ½ PMP storm. A letter from NCDENR dated April 18, 1983 states that NCDENR has approved the design storm for the Dam to be the ½ PMP and that concurrence of the ½ PMP as the appropriate design storm is contingent upon the downstream damageable values remaining as they presently exist. As a result, Schnabel calculated the spillway capacity and design storm to check that NC Dam Safety requirements are met.

Our downstream incremental damage analysis showed that the ½ PMP with breach caused additional downstream impacts when compared to the ½ PMP without breach, thereby requiring an increase in the design storm potentially up to the ¾ PMP. The spillway capacity was evaluated to further determine whether the dam can safely pass either the ½ PMP (current design storm) or ¾ PMP (maximum current regulatory design storm). Our spillway capacity analyses showed that the ½ PMP overtops the parapet wall by 0.7 feet, while the ¾ PMP overtops the earthen embankment by 1.3 feet. Therefore, the spillway capacity is inadequate to safely pass either design storm. Schnabel recommends additional analyses be performed to determine the appropriate design storm and to evaluate alternatives for upgrades for additional spillway capacity to meet State requirements. One upgrade option would likely include raising the embankment and armoring the embankment below the non-overflow section (downstream of the parapet) to protect against erosion of the embankment during overtopping.

NC Dam Safety requires a conduit to drain the reservoir and that the conduit design should include a computation of the minimum time required to drain the reservoir. The underwater inspection found that the current reservoir drains (72” diameter and 36” diameter at invert elevations 264.0 and 270.5, respectively) are currently buried under sediment and debris and are not functional. In addition, the downstream ends of the conduits were blocked off with grouted stone. It is unknown if the interior of the conduits was filled with concrete or if the conduits remain open through the dam.

An alternative for a reservoir drain was analyzed. The hydraulic capacity of using one or more of the sluice gates (60” diameter and 42” diameter both having invert elevations at 291.5) in Bays 1, 2, or 3 as a reservoir drain was estimated. Under an initial normal pool and non-storm conditions, our preliminary analyses showed that the 60” sluice gate (with an invert inlet El. 291.5) drains the reservoir El. 298.5 (two feet above the top of pipe) at an average rate of 5 feet per day. The 42” sluice gate was estimated to drain the reservoir to two feet above the top of pipe at an average rate of 2.5 feet per day. Either sluice


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gate was estimated to have adequate capacity to drawdown the lake. It should be noted that the bends in the pipe were not included in the analysis and would reduce the hydraulic capacity. In addition, mechanical component upgrades would be required for either sluice gate to be used as a reservoir drain. Therefore, a future study is recommended to consider these other factors and assess the feasibility of one or more of the 60” (preferably) or 42” gates for use as reservoir drains. Permanent abandonment of the current reservoir drains is recommended to minimize the risk for future leaking.

3.1.3.2 Embankment Stability Summary

As-built drawings and geotechnical soils testing for the Lake Michie Dam embankment are unable to be found. Therefore, an appropriate stability analysis is unable be performed. To perform a stability analysis, Schnabel recommends a subsurface investigation to estimate geotechnical parameters of the embankment soils. The investigation should also identify the extent of a concrete core wall, which appears to have been constructed in the embankment based on historical photos. The results of the subsurface investigation and stability analysis should be used to determine if a new filter is needed to collect seepage observed downstream of the embankment.

3.1.3.3 Structural Stability Analysis Summary

Schnabel performed a preliminary stability analysis of a typical spillway section of Lake Michie Dam. NC Dam Safety suggests using federal guidelines for the analysis of large dams. Schnabel selected US Army Corps of Engineers (USACE) design manuals, including “Stability Analysis of Concrete Structures”, USACE EM 1110-2-2100 and “Gravity Dam Design”, USACE EM 1110-2-2200. The required minimum factors of safety for sliding stability in accordance with USACE EM 1110-2-2100 guidelines are shown in Table 3-2. The results of our analyses for each loading condition assuming full uplift condition (no pressure relief from the dam drain system) are also shown in Table 3-2.

Table 3-2. Summary of Lake Michie Dam Stability Analysis Results

Load Case Loading Description Calculated Factor of Safety / Required

LC1 Normal Pool 1.41 / 2.0

LC2 Flood Discharge (300-yr storm)

1.02 / 1.5

LC3 Normal Pool w/ OBE 1.35 / 1.7

LC4 Normal Pool w/ MCE 1.12 / 1.3

LC5 3/4 PMP 0.65 / 1.1

None of the analyzed load cases and uplift combinations yielded acceptable factors of safety for the loads and material properties considered. The dam has an internal drainage system and 3 foundation


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piezometers, however, the effectiveness of the drainage system is unknown due to the unreliability of the foundation piezometers. It is possible that foundation uplift pressures under normal operation and flood conditions are significantly less than uplift pressures assumed in the analysis, and it is possible that foundation strengths are higher than assumed in the analysis. The clogged horizontal drain pipes and gallery drainage pipes should be cleaned. The unreliable piezometers should either be rehabilitated or abandoned and new piezometers should be installed. Leaks in the concrete monoliths should be grouted. The working drains, new piezometers, and grouted leaks in the concrete will provide a better estimate of the uplift pressures on the dam to include in the stability analysis.

Once these repairs have been made, Schnabel recommends coring the dam to obtain samples for testing the concrete and foundation. Material properties, including compressive strength, tensile strength, and shear strength at lift lines, will be tested in order to refine the stability analysis. Schnabel’s preliminary stability analysis indicated unacceptable factors of safety for sliding stability along lift lines and it is expected that a dam strengthening program will be required to meet recommended factors of safety. After the material properties have been evaluated, the dam would be reanalyzed and a strengthening program would be designed. The strengthening would likely consist of vertical post-tensioned steel anchors installed from the top of the dam, grouted down into the rock foundation.

3.1.4 Potential Failure Mode Analysis

A Potential Failure Mode Analysis (PFMA) was performed for Lake Michie Dam to evaluate dam safety considerations from a risk perspective. This exercise was intended to identify any potential failure modes for the dam and appurtenant structures that are credible and could result in an uncontrolled release of the reservoir, for a range of loading conditions including normal operations, floods, and earthquakes. Risk estimates were prepared for each potential failure mode based on the estimated probabilities of the load and of the structural response resulting in failure, and on the expected consequences of failure expressed in terms of life loss. Other potential consequences of failure, including property damage and loss of water supply or service, were considered qualitatively. Identification of the potential failure modes and associated risks was necessary to verify that appropriate surveillance, monitoring, maintenance, and risk reduction measures are employed at the site. The PFMA report for Lake Michie Dam is included in Appendix F.

The PFMA report indicates that spillway instability during a large flood event (as analyzed above) is the most critical potential failure mode relative to risk at Lake Michie Dam. Although the existing structure successfully withstood about 7 feet of overtopping in August 1996, the ¾ PMP would result in over 20 feet of overtopping. Insufficient information is currently available to assess the performance of the spillway section under these conditions, and appropriate data collection and risk reduction measures have been recommended, along with continued surveillance and monitoring. The risk of embankment overtopping failure is more than two orders of magnitude smaller due to the embankment crest being 19 feet higher than the spillway crest, and due to the remoteness of the flood event. The existence of the concrete core wall within the embankment section significantly reduces the probability of a potential piping failure. The potential for rupture of a 42-inch water supply pipe and associated reservoir drawdown can be prevented by appropriate inspection and maintenance.


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3.2 Little River Dam

3.2.1 Visual Inspection

The objective of the Little River Dam Inspection task was similar to that described in Section 3.1.1 for Lake Michie Dam. The inspection was conducted on March 13, 2015 and the report is included in Appendix C. All spillway gates were attempted to be operated during the inspection and a summary is shown in the inspection report. The report identified O&M issues observed and recommendations for follow-up engineering studies and/or dam repairs.

Schnabel and a dive inspection team from Glenn Underwater Services performed an underwater inspection on April 16, 2015. The underwater inspection summary is shown in Appendix C. The concrete spillway, riser structure, spillway gates, and other items associated with the spillway were found to be in average condition for a 30-year old dam. The riser structure sluice gates, stems, and stem guides were found to be in good condition but will require thorough cleaning before operating the gates. The trash rack seems to be working in its current condition but was partially clogged with growth and needs to be water-jetted clean. The reservoir drain located on the left side of the intake tower was unable to be fully inspected due to a trash rack encompassing the sluice gate. The City reported that the drain gate has not been operated recently. We recommend routine water-jet cleaning the stop log slots, trash rack, and sluice gates every 5 years to maintain functionality. We recommend performing an underwater survey every 10 years to inspect the condition of the dam and to observe sediment buildup around the intake structure and spillway gates.

3.2.2 Condition Assessment

Similar to the pumping station assessment (as discussed in Section 2.2), dam assets were assigned a condition and performance score based on field observations. Each asset was categorized under an asset group. The following asset groups for Little River Dam are shown below:

Embankment Roller Gates and Stoplogs Spillway Chute Intake Structure Reservoir Tunnel Access Roads and Fencing Instrumentation Dam Electrical Saddle Dam

Condition assessment forms were completed during the field inspection and the forms are organized by asset group. The forms show the scores for each asset and are included in Appendix D. Figure 3-2 shows the distribution of assets for each C&P region.


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Figure 3-2. Little River Assets within C&P Regions

It should be noted that each spillway roller gate was evaluated as a separate asset. Four of the nine roller gates were assigned to C&P region 4. Due to the severe erosion and undermining of the drainage channel, the drainage channel on the embankment is in C&P region 5. In addition, the non-functional lighting in the diversion tunnel is also in C&P region 5. We are currently preparing a proposal to develop plans and specifications for repair of the damaged area. Table 3-3 shows the number of Little River Dam assets within each C&P region.

Table 3-3. Summary of Deficiences by Asset Class for Little River Dam Assets – Number in C&P Region

Asset Class C&P Region 1

C&P Region 2

C&P Region 3

C&P Region 4

C&P Region 5

Little River Embankment 9 1 0 0 1 Little River Roller Gates and Stoplogs 5 5 0 5 0

Little River Spillway Chute 7 3 0 0 0 Little River Intake Structure 6 3 0 1 0

Little River Reservoir 1 0 0 0 0 Little River Tunnel 0 1 0 0 0

Little River Access Roads and Fencing 8 0 0 0 0 Little River Instrumentation 0 2 0 0 0 Little River Dam Electrical 3 0 0 0 1

Little River Saddle Dam 7 0 0 0 0

2

6

0

15

46

0 10 20 30 40 50

C&P Region 5

C&P Region 4

C&P Region 3

C&P Region 2

C&P Region 1

Little River Assets within C&P Region


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3.2.3 Dam Safety Analyses

Schnabel reviewed available reports and analyses for Little River Dam and in some cases performed preliminary engineering analyses to identify potential dam safety deficiencies related to the NC Dam Safety regulatory requirements. The analyses included hydraulic capacity evaluation, and structural stability, and are summarized in the following sections. The technical memorandums are included in Appendix E.

3.2.3.1 Hydrology and Hydraulic Analysis Summary

Schnabel performed a hydrology and hydraulic analysis for Little River Dam to verify the spillway capacity and the gate operations with respect to downstream impacts. NC Dam Safety requires the spillway to safely pass the ¾ PMP design storm. The spillway was designed so when all gates are open, it will safely pass the ¾ PMP flood. Schnabel estimates that the spillway for Little River Dam has a hydraulic capacity of 85,570 cfs with the maximum water at elevation 359.8 feet (5.2 feet below the top of dam) when all nine gates are fully open.

At the time of the March 2015 annual dam inspection, only four gates out of the nine were operational. Therefore, we analyzed the spillway capacity when only four gates are completely open. The spillway was estimated to pass 37,900 cfs with four gates completely open and the reservoir water surface at the crest of the dam.

The results of our analyses indicate that there are no impacted structures (without consideration of structures along the back waters) downstream of the dam when there is a flow release from Little River Dam of up to 4,800 cfs. If there is a flow release from the dam greater than 4,800 cfs, the Railroad crossing located about 3.5 miles downstream of the dam gets overtopped.

Schnabel recommends replacing all of the gate actuators as soon as possible because the spillway does not satisfy NC Dam Safety spillway capacity criteria without full operation of all gates.

We also recommend an analysis of the inundation zone upstream of dam for the design storm. Assets upstream of the dam may be inundated (e.g. bridge overtopping) and may need to be considered in gate operations and an updated Emergency Action Plan.

3.2.3.2 Slope Stability Analysis Summary

Schnabel performed a slope stability analyses to check that NC Dam Safety requirements are met. NC Dam Safety regulations require a minimum slope stability factor of safety of 1.5 for normal loading conditions, and 1.25 for rapid drawdown. The slope stability analysis for Little River Dam indicated that one upstream slope stability section does not meet stability requirements for the rapid drawdown condition (Load Condition 3). The calculated factor of safety was 1.0 compared to the 1.25 factor of safety required by the State. The analysis for Load Condition 3 was conservative where the lowering of the phreatic surface over time as the reservoir level declines was not modeled. A refinement to the analysis accounting for the lowering of the phreatic surface may indicate an acceptable factor of safety. Schnabel recommends performing a transient seepage analysis and updating the rapid drawdown stability model to verify if the calculated stability factor of safety can be increased.


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3.2.4 Potential Failure Mode Analysis

A Potential Failure Mode Analysis (PFMA) was performed for Little River Dam to evaluate dam safety considerations from a risk perspective. This exercise was intended to identify any potential failure modes for the dam and appurtenant structures that are credible and could result in an uncontrolled release of the reservoir, for a range of loading conditions including normal operations, floods, and earthquakes. Risk estimates were prepared for each potential failure mode based on the estimated probabilities of the load and of the structural response resulting in failure, and on the expected consequences of failure expressed in terms of life loss. Other potential consequences of failure, including property damage and loss of water supply or service, were considered qualitatively. Identification of the potential failure modes and associated risks was necessary to verify that appropriate surveillance, monitoring, maintenance, and risk reduction measures are employed at the site. The PFMA report for Little River Dam is included in Appendix F.

The PFMA report indicates that the most critical potential failure modes relative to risk at Little River Dam are related to piping or internal erosion at various locations within the main embankment under normal operating conditions, which would warrant continued monitoring of the existing piezometers and seepage collection stations for any changes. Recommended levels of inspection, monitoring, and maintenance for these potential failure modes should provide sufficient risk reduction. In addition, the increased risk of piping under higher reservoir levels associated with a large flood is more than offset by the reduced probability of the flood loading. The risk of overtopping failure of either the main embankment or the saddle dam during a large flood is wholly contingent upon the condition of the spillway gates, and is considered extremely remote with their proper operation and maintenance. Although the concrete spillway chute structure has sufficient defensive design measures to minimize the potential for slab jacking failure due to uplift pressures, future inspections of the spillway outlet slabs should be performed in the dry whenever possible to observe the condition of the concrete surfaces and floor joints. The potential for rupture of the 72-inch water supply pipe and associated reservoir drawdown can be prevented by appropriate surveillance and maintenance.

4.0 CONSEQUENCE ANALYSIS

4.1 Approach

Eight evaluation factors were considered in establishing the consequence of failure for the various assets evaluated. For the purposes of this evaluation, the factors are defined as follows:

Emergency Operation – The asset is required for operation of the dam and raw water pumping station when an emergency or natural disaster is ongoing (e.g., hurricane).

Ease of Maintenance/Repair – The asset’s access for maintenance and repair is limited, or requires parts which must be special ordered.

Regulatory Compliance – The asset is required to operate for the facility to comply with regulatory requirements, including regulations applying to facility operation, to treated water quality and to environmental protection.

Health & Safety – Failure of the asset would adversely impact employee or public health and safety.

Meet Public/Community Level of Service – The asset is required for the City to meet community level of service commitments – e.g., quantity, reliability


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Response Time – Prompt response to repair the asset is required – no asset redundancy, and asset may not be out of service for more than a brief time.

Financial Impact if Asset Fails – When failure occurs, the asset will be costly to repair, or may cause damage to property which would be City’s responsibility.

The score for an individual consequence parameter is equal to its selected Rank multiplied by a weighting factor as discussed in more depth below.

4.2 Pairwise Comparison

The Consequence of Failure assessment for the asset groups at DWM’s two raw water supply facilities was accomplished using a “pairwise comparison” approach. In this approach, two entities are compared head-to-head and judged as to which is preferred according to a measured property. In this application, pairwise comparisons are utilized in two stages of the analysis:

The relative importance of the raw water supply facility asset groups for each individual evaluation criterion.

The relative importance of each evaluation criteria, to establish weighting factors needed for the Consequence of Failure scores

In the pairwise comparison approach used in this project, 1 point is available to be allocated for each comparison. Two entities are compared with regard to relative importance (e.g., two asset groups – “pumps” versus “sluice gates”; two evaluation criteria – “emergency operation” versus “financial impact if asset fails”). One point can be assigned to either asset group or evaluation criteria, based on judged comparison, or if the two entities are judged to be equally important, then 0.5 points are assigned to each. For example:

“Pumps” and “sluice gates” asset groups are compared with regards to the “ease of maintenance” evaluation criterion. Specifically, the comparison being judged is for which asset group is limited access for maintenance and repair, or special-order spare parts, is more of an issue. In this example, pumps and sluice gates are viewed as equally critical when ease of maintenance issues are considered, so each is assigned 0.5 points.

“Emergency operation” and “financial impact if asset fails” are compared in order to judge which criterion is more important to establishing the consequence of an asset failure. This is a general evaluation, considering all asset groups. In this example, emergency operation is viewed as more critical to establishing the consequences of an asset failure, and is assigned 1 point.

4.3 Weighting Consequence Evaluation Criteria

The results of the pairwise comparison of the 8 evaluation criteria for the DWM dams/raw water pumping station assets are presented below. “Health & Safety” and “Meet Community Level of Service” scored the highest; “Financial Impact if Asset Fails”, while important, achieved the lowest score in the pairwise comparison exercise. To facilitate using the pairwise comparison of evaluation criteria as weighting factors, the criteria scores were normalized to a maximum score of 10 and a minimum score of 1.


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Table 4-1. Pairwise Comparison of Consequence Evaluation Criteria

Evaluation Criteria Rank Weight

Health & Safety 1 10

Meet Community Level of Service 1 10

Emergency Operation 3 8

Response Time 4 6

Ease of Maintenance/Repair 5 5

Regulatory Compliance 6 2

Financial Impact if Asset Fails 7 1


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4.4 Pumping Station Results

Table 4-2 summarizes the results of this assessment, and the individual asset group pairwise comparison tables for each evaluation criterion are presented in Appendix G.

Table 4-2. Pairwise Comparison of Dam/Raw Water Pumping Station Asset Groups

Emer

genc

y Op

erat

ion

Ease

of

Mai

nten

ance

Regu

lato

ry Co

mpl

ianc

e

Heal

th &

Sa

fety

Com

mun

ity

Leve

l of S

ervic

e

Resp

onse

Tim

e

Finan

cial

Impa

ct

Wei

ghte

d Co

nseq

uenc

e Sc

ore

Norm

alize

d Sc

ore

(Max

=50)

Rank

Category Weight 8 5 2 10 10 6 1 Asset Groups Individual Evaluation Criterion Scores

Dam 17.5 17.5 17.5 17.5 17.5 17.5 17.5 735 50 1 Spillway 17.5 17.5 17.5 17.5 17.5 17.5 17.5 735 50 1

Intake Structure 16 16 16 15 15.5 16 16 657 45 3 Plant Electrical 12 10.5 8 15 12.5 12.5 9 524 36 4

Pump 14 12 12.5 11.5 13 11.5 11.5 523 36 5 Sluice Gate 13 14 13 8.5 12.5 12 10.5 493 34 6

Valves 12 11 9.5 11 10.5 11.5 8 462 31 7 Motor 12 9 10 7 12.5 9.5 12 425 29 8

Destratification System

6 11 12 8 11 10 5 382 26 9

Piping 12 9.5 9.5 5 9.5 11 8.5 382 26 9 Emergency Generator 7.5 1 6 14 7 5 7 324 22 11

Compressor 3 2 6 9 8 7.5 2.5 264 18 12 Oil Accumulator

System 8 6.5 4.5 4 5 5.5 3 232 16 13

Building/ Civil

4.5 6.5 1 9.5 2 2 13.5 211 14 14

Bar Rack 2 10.5 3 5 4 5.5 10 208 14 15 Flow Meter 6 3.5 11 2 5.5 7 2.5 207 14 16

Crane 4 7 2 10 1 2 12.5 206 14 17 Instrument 4 2.5 11 1.5 5.5 6.5 2.5 178 12 18

HVAC 0 3 0.5 0 0 0 2 21 1 19

When all evaluation criteria are considered, the two highest-consequence asset groups are the dams and spillways, each assigned the maximum normalized Consequence of Failure score of 50. These two asset groups were favored in each pairwise comparison, except when compared to each other, when they were given equal scores. The intake structures were a close third rank, with a normalized Consequence of Failure score of 45.

The pairwise comparison approach considered whether any difference in consequence of failure exists between the Lake Michie Dam assets and the Little River Dam assets. It was considered that both dams and raw water pumping facilities are equally consequential to the utility meeting its level of service requirements, so both Lake Michie and Little River facilities were assigned equal consequence of failure. This does not imply that the risk/criticality scores of assets at the two facilities would be equal. Given the differences in facility age and observed condition during the 2015 condition assessments, the Likelihood


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of Failure for Lake Michie assets might be generally described as higher, yielding a higher risk score for a Lake Michie Dam asset compared with a similar asset at Little River Dam.

4.5 Dam Results

The dams at Lake Michie and Little River were further divided into asset groups to evaluate the various components. The following asset groups are represented at Lake Michie Dam:

Embankment Concrete Gravity Dam Spillway Outlet Works Trailrace and Draft Tubes Reservoir Access and Fencing Instrumentation Dam Electrical

The following asset groups are represented at Little River Dam:

Embankment Roller Gates and Stoplogs Spillway Chute Intake Structure Reservoir Tunnel Access Roads and Fencing Instrumentation Dam Electrical Saddle Dam

The pairwise comparison approach was applied to each of the dam asset groups for each of the 8 evaluation criteria. The pairwise analysis included a comparison of assets between each dam, so, for example, the importance of the Lake Michie Embankment was compared to the Little River Embankment for each of the 8 evaluation criteria. The summed scores under each category for each criteria was weighted based on the values shown in Table 4-1 and then summed to obtain a weighted consequence score. The weighted consequence score was then normalized to a high score of 50. The scores were then ranked and are shown in Table 4-3 in descending order.


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Table 4-3. Summary of Consequence Assessment Results

Asset Class Weighted

Consequence Score

Normalized to High Score 50 Rank

Little River Roller Gates and Stop Logs 582 50 1 Michie Embankment 573 49 2

Little River Spillway Chute 572 49 3 Little River Embankment 557 48 4

Michie Concrete Gravity Dam 546 47 5 Michie Spillway 546 47 5

Little River Tunnel 530 46 7 Little River Saddle Dam 495 43 8

Michie Outlet Works 491 42 9 Little River Intake Structure 487 42 10

Michie Tailrace and Draft Tubes 286 25 11 Michie Instrumentation 204 17 12

Little River Instrumentation 204 17 12 Little River Dam Electrical 167 14 14

Little River Access Roads and Fencing 166 14 15 Michie Dam Electrical 153 13 16

Michie Access and Fencing 150 13 17 Little River Reservoir 135 12 18

Michie Reservoir 134 12 19

5.0 RISK ASSESSMENT

5.1 Risk Assessment Approach

Risk, sometimes expressed as “criticality” is expressed as a function of (1) the “likelihood” that a utility asset will fail to meet its level of service requirement, and (2) the “consequence” this asset failure would represent.

RISK = Likelihood of Failure x Consequence of Failure

Risk and the perception of risk permeate asset decision making. Most decisions on preventive maintenance, refurbishment, and replacement are typically made to avoid the risk of unexpected asset failure. Even decisions regarding expansions, improvements, and new facilities are usually made to reduce risk—risk of not meeting growth in demand, risk of failing to comply with regulatory guidelines, or risk of experiencing incidents with consequences for public health or employee safety.

Schnabel and BC developed a risk model to assess the criticality of the Lake Michie and Little River dam and pumping station facilities.


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The Condition and Performance rankings for each dam and pumping station asset, which were determined during the site visits, represent the “Likelihood of Failure” side of the equation. This is discussed in Section 2 and 3.

“Consequence of Failure” comparative rankings for each system at both facilities were developed following a pairwise comparison approach, assessing the relative consequence of system consequence of failure, considering factors such as emergency operation, ease of maintenance/repair, vulnerability to catastrophic failure, to assist prioritization of repairs and rehabilitation projects. This is discussed in Section 4.

As noted above, for each asset group, the risk score is calculated as the product of Likelihood of Failure with Consequence of Failure. The maximum score for Likelihood and Consequence are each 50, and the maximum risk score is 50 x 50 = 2500.

For example, the Likelihood of Failure of the Little River oil accumulator system was calculated as 40. Table 3 of Appendix H.1 indicates the Consequence of Failure for the “Oil Accumulator System” asset group is 16. The resulting risk score of this asset is 40 x 16 = 640.

5.2 Risk Assessment Results

Appendix H lists the likelihood of failure, consequence of failure, and overall risk/criticality scores for each raw water pumping station asset evaluated at Lake Michie Dam and Little River, organized according to asset group.

Figure 5-1 plots the likelihood of failure and consequence of failure scores, with a delineation of scores as higher, moderate or lower risk.

Figure 5-1. Scatter Graph Distribution of Pumping Station Risk Assessment Scores


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As shown on the Figure 5-1 scatter plot, natural breaks in the calculated risk scores were observed around the 10th percentile, risk score 900 (designated as the break between “high risk” and “moderate risk” on the scatter plot) and around the 29th percentile, risk score 400 (designated as the break between “moderate risk” and “low risk”). The highest criticality/risk raw water pump station assets based on the criticality scoring were determined to be:

Lake Michie Hydro Turbine and Pump No. 2 Lake Michie Medium Voltage Electrical Equipment Lake Michie Electric-Driven Pumps

As stated previously, the risk scores reflect the condition and performance of assets at the time the analysis was performed, and changes in asset condition or consequence would be expected to impact the criticality scores.

Appendix H contains a table that lists the likelihood of failure, consequence of failure and overall risk/criticality scores for the dam related assets evaluated at Lake Michie Dam and Little River. The table is sorted with the highest risk item at the top.

Figure 5-2 plots the likelihood of failure and consequence of failure scores, with a delineation of scores as higher, moderate or lower risk for dam assets. More dam assets plot at a high consequence of failure compared to the pumping stations assets. This is because during the pairwise consequence comparison, the dam and spillway was always ranked above the pumping station assets. As such, the break in the calculated risk scores was assigned at a higher risk score of 1800 (designated as the break between “high risk” and “moderate risk” on the scatter plot) and at risk score 400 (designated as the break between “moderate risk” and “low risk”). The break between high and moderate risk on a different scale than the pumping stations provides a grouping of high risk assets related to a high condition and performance region, not just assets that would be higher consequence.


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Figure 5-2. Scatter Graph Distribution of Dams Risk Assessment Scores

For the dam assets, more assets plot with a higher consequence of failure. The majority of the dam assets fall under the low to moderate risk category. The high risk dam assets based on the risk scoring were determined to be:

Lake Michie Embankment Drainage System Little River Drainage Channel Lake Michie Trash Rake Little River Roller Gates #4, #5, #7, #8 Little River Stoplog Monorail System

These assets that full under the high risk category are related to a dam safety issue, either with the stability, hydraulic capacity, or potential failure mode of the dam. These assets should be addressed as a high priority in the early stages of the 10-year CIP projects.


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6.0 REHABILITATION PLAN

The City, assisted by Schnabel and Brown and Caldwell, reviewed the risk assessment findings and the observed deficiencies at each dam asset to develop a list of repairs and operation and maintenance actions in order of priority. Dam Safety issues were given highest priority. All Dam Safety issues must be resolved for the dam to be compliant with NC Dam Safety regulations. For other deficiencies, the risk scores, along with each asset’s deficiency C&P region were the basis for the prioritization of capital improvement and O&M rehabilitation projects.

The rehabilitation plan includes a 50-year prioritized rehabilitation and replacement plan for the two dams and the raw water pumping stations, addressing both projects related to addressing current condition/performance deficiencies, and service life replacements within the planning horizon for Fiscal Years 2016-2065.

The rehabilitation plan includes a 10-year Capital Improvement Plan (FY 2016-2025) to address the near term deficiencies identified.

Work orders are generally smaller tasks that are expected to be completed using City personnel. The cost of these tasks is not included in the Rehabilitation Plan.

The complete list of Rehabilitation Plan recommendations is included in Appendix I for the pumping stations and Appendix J for the dams.

6.1 Recommended Rehabilitation Plan Projects

Schnabel recommends approximately 85 assets receive further attention to address observed deficiencies. Brown and Caldwell recommends approximately 121 pumping station assets receive further attention to address observed deficiencies. The recommendations range from periodic re-inspection and preventive maintenance work orders, to small repair projects which could be accomplished with in-house staff or contractors, to capital projects addressing a major deficiency or replacement for an asset at the end of its service life.

6.2 Prioritizing Capital Improvement and Work Order Projects

The City of Durham plans to structure its improvements plan to address observed asset deficiencies by one of two project types:

Capital Project – Utility Engineering Administered Projects for Asset Rehabilitation/Replacement Work Orders Performed by DWM Personnel

Capital Projects were assigned a recommended year for implementation, scheduling the highest risk items first. Dam Safety issues generally have highest risk scores and were scheduled early in the 10-year CIP. Some issues require further investigation to reduce the uncertainty in recommendations and to develop the most appropriate and economical plan of action. Work Orders are relatively small in scope and are expected to be performed with DWM personnel. For the purpose of this Rehabilitation Plan, they are assumed to already be funded through DWM’s normal


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operating budget. Work Orders for the pumping stations were not assigned a recommended year for implementation. It is expected that all pumping station Work Orders will be completed in the first 3 years (by the end of FY 2018), performing the highest-risk items first. The timing of some of the dam Work Orders is critical as these tasks are precursors to larger Capital Projects. These Work Orders have been assigned a recommended year for implementation. Work Orders have been assigned to specific divisions within DWM to clarify responsibility. In the event these Work Orders cannot be completed by DWM personnel, it is expected that these tasks would be completed by hiring a Contractor.

6.3 Planning-Level Cost Estimating Approach

Schnabel and Brown and Caldwell developed preliminary planning-level opinions of probable cost for engineering and construction of recommended Capital Projects and Operations and Maintenance Projects. In accordance with the Association for the Advancement of Cost Engineering International (AACE) criteria, this is a Class 5 estimate. A Class 5 estimate is defined as a conceptual-level estimate. Typically, the project engineering is 0 to 2 percent complete. Class 5 estimates are used to prepare planning-level cost scopes or evaluation of alternative approaches, long-range capital outlay planning and as the basis for more detailed Class 4 estimates. Expected accuracy of Class 5 estimates typically range from -50 percent to +100 percent, depending on the technological complexity of the project, appropriate reference information, and the inclusion of appropriate contingency determination.

Conceptual-level opinions of probable cost were based upon readily-available information without engineering design, including quantity take-offs, vendor quotes, recently awarded projects, cost tables, and allowances. Where the City has multiple options to address deficiencies, such as for ventilation of Lake Michie pumping station electrical gear, the cost of the more expensive alternative has been included. Cost opinions included a 30-percent contingency. A typical planning/design allowance of 10 percent to 15 percent is applied only to projects where these tasks would be required. For example, the planning/design allowance is not applied to the on-call contractor tasks. Where hydraulic modeling studies or engineering alternatives analysis is anticipated prior to a design-bid-build project to address an observed deficiency, the cost of these studies are estimated. The cost estimates assume no subsurface or geotechnical issues except where explicitly stated.

Dam Safety related projects are scheduled first. Other projects and on-call contracts are programmed to be performed at the high-risk assets first, with a goal to complete projects to address current C&P Region 3/4/5 deficiencies within the first 4 to 5 years of the 10-year Capital Improvements Plan for FY2016-FY2025 (that is, by 2021).

All costs were estimated in 2015 U.S. Dollars. No cost escalation was applied to future projects over the 50-year planning period.

6.4 Prioritized List of Capital Improvement and O&M Projects

Schnabel organized the 197 individual dam asset recommendations according to this approach, into 42 Capital Projects (29 projects at Lake Michie and 13 projects at Little River). Brown and Caldwell organized the 121 individual pumping station asset recommendations into 29 Capital Projects (17 projects at Lake Michie and 12 projects at Little River). Some deficiencies, such as the spillway capacity and stability issues, do not satisfy current state Dam Safety criteria. These are summarized in Table 6-1, Table 6-2, Table 6-3, and Table 6-4 below, with descriptions of each project and the allocation of funding by budget year included in Appendix I and Appendix J. Figure 6-1 shows preliminary estimated funding


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allocated over the next 10 years to address the highest priority observed dam and pumping station deficiencies. Figure 6-2 shows preliminary estimated funding allocated for all projects in the 50-Year planning horizon with the exception of Work Orders, which will be performed by DWM personnel.

Figure 6-1. Preliminary Estimate of Expenditures in 10-Year CIP

Figure 6-2. Preliminary Estimate of Total Expenditures in 5-Year Increments for 50-Year Plan


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Additional information on the cost estimates are summarized in Appendix I for the pumping stations and Appendix J for the dams. The Capital Improvements Plan recommended projects begin in FY2015-16, which started July 1, 2015, so that the costs of these projects may be allocated through the City’s normal budget process.


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Table 6-1. Prioritized Capital Improvement Projects for Pumping Stations Rehabilitation

Summary by Project

No. Project FY2015-16 FY2016-17 FY2017-18 FY2018-19 FY2019-20 FY2020-21 FY2021-22 FY2022-23 FY2023-24 FY2024-25 Total Request

CIP-LMPS-1 Lake Michie Emergency Generator Upgrade $0 $726,000 $726,000 $0 $0 $0 $0 $0 $0 $0 $1,452,000

CIP-LMPS-2 Lake Michie Electrical Equipment Replacements $0 $303,500 $303,500 $0 $0 $0 $0 $0 $0 $0 $607,000

CIP-LMPS-3

Lake Michie Incoming Electrical Feed Improvements (Allowance, Pay to Duke Energy)

$0 $150,000 $0 $0 $0 $0 $0 $0 $0 $0 $150,000

CIP-LRPS-1 Little River Electrical Panel Replacements $0 $16,000 $0 $0 $0 $0 $0 $0 $0 $0 $16,000

CIP-LRPS-2 Little River Pump Inspections/Repairs $0 $46,000 $0 $0 $0 $0 $0 $0 $0 $0 $46,000

CIP-LRPS-3 Little River Emergency Generator Upgrade $0 $433,000 $433,000 $0 $0 $0 $0 $0 $0 $0 $866,000

CIP-LRPS-6

Little River Thermal Destratification Compressor Replacement

$0 $25,000 $0 $0 $0 $0 $0 $0 $0 $0 $25,000

CIP-LMPS-9 Lake Michie Pumping Station Roof Replacements $0 $176,500 $176,500 $0 $0 $0 $0 $0 $0 $0 $353,000

CIP-LMPS-5

Lake Michie Thermal Destratification System Replacement

$0 $560,000 $0 $0 $0 $0 $0 $0 $0 $0 $560,000

CIP-LMPS-4 Lake Michie Valve/Actuator Rehab $0 $0 $298,000 $298,000 $0 $0 $0 $0 $0 $0 $596,000

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Summary by Project


CIP-LRPS-7

Little River Roof Replacements (Pumping Station, Intake Structure, Stop Log Bldg)

$0 $0 $364,000 $0 $0 $0 $0 $0 $0 $0 $364,000

CIP-LRPS-11 Little River 54-inch Valve Installation $0 $0 $125,000 $0 $0 $0 $0 $0 $0 $0 $125,000

CIP-LMPS-8 Lake Michie Piping/Conduit Corrosion Inspections $0 $0 $0 $50,000 $0 $0 $0 $0 $0 $0 $50,000

CIP-LMPS-7

Lake Michie Piping/Pumps/Valves Coatings Replacement

$0 $0 $0 $126,000 $0 $0 $0 $0 $0 $0 $126,000

CIP-LRPS-5 Little River Piping/Conduit Coatings Replacements $0 $0 $0 $121,000 $0 $0 $0 $0 $0 $0 $121,000

CIP-LMPS-13

Lake Michie Potable Water Supply & Septic System Rehabilitation

$0 $0 $0 $50,000 $0 $0 $0 $0 $0 $0 $50,000

CIP-LRPS-12 Little River Potable Water Supply $0 $0 $0 $15,000 $0 $0 $0 $0 $0 $0 $15,000

CIP-LRPS-8

Little River Control Valve/Actuator Rehab (CV201, CV301, CV401)

$0 $0 $0 $0 $0 $76,000 $0 $0 $0 $0 $76,000

CIP-LMPS-10

Lake Michie Pumping Station Repainting, Lead Paint Abatement

$0 $0 $0 $0 $0 $304,000 $0 $0 $0 $0 $304,000

CIP-LMPS-11 Lake Michie Pumping Station Window Replacements $0 $0 $0 $0 $0 $138,000 $0 $0 $0 $0 $138,000

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Summary by Project


CIP-LMPS-12

Lake Michie Pumping Station Ventilation System (Fan/Louver Ventilation Alternative)

$0 $0 $0 $0 $0 $1,178,000 $0 $0 $0 $0 $1,178,000

CIP-LMPS-14 Lake Michie Elevator Rehabilitation $0 $0 $0 $0 $0 $0 $196,000 $0 $0 $0 $196,000

CIP-LMPS-16 Lake Michie Structural Concrete Repairs $0 $0 $0 $0 $0 $0 $36,000 $0 $0 $0 $36,000

CIP-LMPS-15

Lake Michie Bridge Crane/Hoist System Improvements

$0 $0 $0 $0 $0 $0 $25,000 $0 $0 $0 $25,000

CIP-LMPS-17 Lake Michie Pumping Station Asbestos Removal $0 $0 $0 $0 $0 $0 $5,000 $0 $0 $0 $5,000

CIP-LRPS-9 Little River Structural Concrete Repairs $0 $0 $0 $0 $0 $0 $75,000 $0 $0 $0 $75,000

CIP-LRPS-10 Little River Stop Log Bldg Re-painting $0 $0 $0 $0 $0 $0 $5,000 $0 $0 $0 $5,000

CIP-LMPS-6 Lake Michie Electric Pump/Motor Replacements $0 $0 $0 $0 $0 $0 $0 $0 $1,938,000 $0 $1,938,000

CIP-LRPS-4 Little River Electric Pump/Motor Replacements $0 $0 $0 $0 $0 $0 $0 $0 $0 $1,463,000 $1,463,000

TOTAL, ALL PUMPING STATION

CIP PROJECTS $0

$2,436,000 $2,426,000 $660,000 $0 $1,696,000 $342,000 $0 $1,938,000 $1,463,000 $10,961,000

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Table 6-2. Prioritized Capital Improvement Projects for Dams Rehabilitation

Summary by Project


CIP-LMD-1 Lake Michie Core Wall Investigation and Tree Removal $ 75,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 75,000

CIP-LMD-2 Lake Michie Incremental Damage Analysis to Determine Design Storm

$ 20,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 20,000

CIP-LMD-3 Lake Michie Subsurface Investigation and Embankment Stability Analysis

$ 40,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 40,000

CIP-LMD-4 Lake Michie Embankment Filter - Design $ 15,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 15,000

CIP-LRD-1 Little River Concrete Drainage Ditch Repair $ 85,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 85,000

CIP-LRD-2 Little River Spillway Gate Operator Replacement $ 210,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 210,000

CIP-LMD-5 Lake Michie Sluice Gates No. 1 and 2 Abandonment - Analysis $ 60,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 60,000

CIP-LRD-3 Little River Embankment Seepage and Stability Analysis $ 7,500 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 7,500

CIP-LRD-4 Little River Inundation Zone Analysis $ 5,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 5,000

CIP-LRD-5 Little River Emergency Action Plan Update $ 15,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 15,000


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Summary by Project


CIP-LMD-6 Lake Michie Material Sampling and Testing and Piezometer Rehab

$0 $ 350,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 350,000

CIP-LMD-7 Lake Michie Concrete Monolith Grouting $0 $ 210,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 210,000

CIP-LMD-8 Lake Michie Spillway Stability Rehab Analysis $0 $ 280,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 280,000

CIP-LMD-9 Lake Michie Embankment Filter - Construction $0 $ 80,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 80,000

CIP-LMD-10 Lake Michie Trash Rack Bar Screen and Stop Log Replacement - Design

$0 $ 80,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 80,000

CIP-LMD-11 Lake Michie Right Concrete Tailrace Wall Investigation $0 $ 40,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 40,000

CIP-LMD-12 Lake Michie Gallery Inflow Monitoring $0 $ 35,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 35,000

CIP-LMD-13 Lake Michie Spillway Apron Repairs - Design $0 $ 65,000 $0 $0 $0 $0 $0 $0 $0 $0 $ 65,000

CIP-LMD-14 Lake Michie Trash Rack Bar Screen and Stop Log Replacement - Construction

$0 $0 $ 465,000 $0 $0 $0 $0 $0 $0 $0 $ 465,000

CIP-LMD-15 Lake Michie Decommission Trash Rake $0 $0 $ 45,000 $0 $0 $0 $0 $0 $0 $0 $ 45,000

CIP-LMD-16 Lake Michie Intake Sluice Gate Replacements - Design $0 $0 $ 160,000 $0 $0 $0 $0 $0 $0 $0 $ 160,000


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Summary by Project


CIP-LMD-17 Lake Michie Sluice Gates No. 1 and 2 Abandonment - Construction

$0 $0 $ 150,000 $0 $0 $0 $0 $0 $0 $0 $ 150,000

CIP-LRD-6

Little River Left Spillway Approach Wing Wall, Piezometers, Right Spillway Training Wall Survey Monuments, and Survey Monitoring Points SM-1 Thru SM-6

$0 $0 $ 45,700 $0 $0 $0 $0 $0 $0 $0 $ 45,700

CIP-LRD-7 Little River Left Spillway Sidewall Repairs $0 $0 $ 50,000 $0 $0 $0 $0 $0 $0 $0 $ 50,000

CIP-LMD-18 Lake Michie General Concrete Repairs - Design $0 $0 $ 140,000 $0 $0 $0 $0 $0 $0 $0 $ 140,000

CIP-LRD-8 Little River Vegetation Removal at Saddle Dam $0 $0 $ 20,000 $0 $0 $0 $0 $0 $0 $0 $ 20,000

CIP-LRD-9 Little River Survey Monitoring $0 $0 $ 4,000 $0 $0 $0 $0 $0 $0 $0 $ 4,000

CIP-LMD-19 Lake Michie Spillway Capacity Improvements - Design $0 $0 $0 $ 225,000 $0 $0 $0 $0 $0 $0 $ 225,000

CIP-LMD-20 Lake Michie Post-Tensioned Anchor Installation $0 $0 $0 $ 2,500,000 $0 $0 $0 $0 $0 $0 $ 2,500,000

CIP-LMD-21 Lake Michie Right Concrete Tailrace Wall Repair $0 $0 $0 $ 350,000 $0 $0 $0 $0 $0 $0 $ 350,000

CIP-LMD-22 Lake Michie General Concrete Repairs - Construction $0 $0 $0 $ 1,200,000 $0 $0 $0 $0 $0 $0 $ 1,200,000


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Summary by Project


CIP-LMD-23 Lake Michie Spillway Capacity Improvements - Construction $0 $0 $0 $0 $ 2,300,000 $0 $0 $0 $0 $0 $ 2,300,000

CIP-LMD-24 Lake Michie Intake Sluice Gate Replacements - Construction $0 $0 $0 $0 $ 1,100,000 $0 $0 $0 $0 $0 $ 1,100,000

CIP-LMD-25 Lake Michie Spillway Apron Repairs - Construction $0 $0 $0 $0 $ 650,000 $0 $0 $0 $0 $0 $ 650,000

CIP-LRD-10 Little River Tunnel Repairs $0 $0 $0 $0 $ 141,000 $0 $0 $0 $0 $0 $ 141,000

CIP-LMD-26 Lake Michie SCADA and Security System $0 $0 $0 $0 $ 140,000 $0 $0 $0 $0 $0 $ 140,000

CIP-LRD-11 Little River SCADA and Security System $0 $0 $0 $0 $ 100,000 $0 $0 $0 $0 $0 $ 100,000

CIP-LRD-12 Little River Upstream Slope Erosion Protection $0 $0 $0 $0 $0 $ 300,000 $0 $0 $0 $0 $ 300,000

CIP-LMD-27 Lake Michie Bathymetry and Study of Sedimentation $0 $0 $0 $0 $0 $0 $0 $0 $ 20,000 $0 $ 20,000

CIP-LMD-28 Lake Michie Removal of Sediment $0 $0 $0 $0 $0 $0 $0 $0 $ 100,000 $0 $ 100,000

CIP-LRD-13 Little River Road Resurfacing $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 100,000 $ 100,000

CIP-LMD-29 Lake Michie Road Resurfacing $0 $0 $0 $0 $0 $0 $0 $0 $0 $ 75,000 $ 75,000

TOTAL, ALL DAM CIP

PROJECTS $532,500 $1,140,000 $1,079,700 $4,275,000 $4,431,0000 $300,000 $0 $0 $120,000 $175,000 $12,053,200


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Table 6-3. Lake Michie and Little River Pumping Stations Rehabilitation Plan Capital Improvement Project Descriptions

ID No. Project Title Project Description High Asset Risk Score

Fiscal Year

Total Budget ($)


CIP-LMPS-1 Lake Michie Emergency Generator Upgrade

Project provides 1,500 KW emergency generator capable of operating largest electrical pump and other Pumping Station facilities 1781 2017 $1,452,000

CIP-LMPS-2 Lake Michie Electrical Equipment Replacements

Project would replace all medium voltage equipment (switchgear, automatic transfer switch, MCC, etc.) and wiring at Lake Michie Pumping Station. Install new power distribution panel for electrical loads associated with future conversion from hydraulic to electric valve actuators. Project provides selective demolition of unused electrical panels and flow indicator-totalizers, including removal from the Pumping Station. Project also replaces several electrical panels at end of their service lives, including power distribution panels, QC Load Center, pull boxes, lighting panels and control panels

1777 2017 $607,000

CIP-LMPS-3 Lake Michie Incoming Electrical Feed Improvements

Allowance for project to compensate Duke Energy for engineering and construction cost to upgrade the incoming electrical feed for Lake Michie, including two isolated transformers

1777 2017 $150,000

CIP-LMPS-4 Lake Michie Valve/Actuator Rehab

Project would replace valves at the end of their service life (Lake Michie valves 1, 2, 3, 16, 19, 20, 22, 23, 24; surge arrester valves 1 & 2); replace packing on Lake Michie valves 17, 21; replace hydraulic actuators with electric actuators (Lake Michie valves 1, 2, 3, 6, 7, 12, 13, 16, 17, 18); Repair/replace discharge worm gears for Valves 14 & 15.

1692 2018 $596,000

CIP-LMPS-5 Lake Michie Thermal Destratification System Replacement

Project demolishes existing thermal destratification system and installs new system. Project will consider installation of newer destratification technologies such as SolarBee.

1039 2017 $560,000

CIP-LMPS-6 Lake Michie Electric Pump/Motor Replacements

Project replaces Electric Pumps/Motors, installed in 1964, at end of their service life. Electric Pump No. 1 will be replaced in-kind, and Electric Pump No. 2 will be increased to 1250 HP, capacity 20,833 GPM to provided redundancy for Pump No. 1 at future system water demand requirements.

712 2024 $1,938,000

CIP-LMPS-7 Lake Michie Piping/Pumps/Valves Coatings Replacements

Project replaces degraded coatings on Hydro and Electrical Pumps, exposed piping and conduit, and valves. Project also completes cleaning, abrasive-blasting, priming and painting of grating supports, and installation of grating and supports. The gratings are currently at Lake Michie Pumping Station, but not installed.

712 2019 $126,000

CIP-LMPS-8 Lake Michie Piping/Conduit Corrosion Inspections

Project provides contractor inspection of corrosion on exposed electrical conduit, piping and valves in Pumping Station 620 2019 $50,000


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Fiscal Year

Total Budget ($)


CIP-LMPS-9 Lake Michie Pumping Station Roof Replacements

Project would replace roofs for Lake Michie Pumping Station and Elevator Penthouse. City's standard roof design utilizes light-weight insulated concrete (LWIC) fill assembly with two-ply modified bitumen membrane roof, with new sheet-metal flashings and accessories. Roofs are 7,056 SF and 375 SF, respectively. City has selected a design consultant for the roof replacement project.

431 2017 $353,000

CIP-LMPS-10 Lake Michie Pumping Station Repainting, Lead Paint Abatement

Project encapsulates/paints Lake Michie Pumping Station and Elevator Penthouse interior (total painted area approx. 27,000 SF). Abatement for existing lead-based wall paint provided as required; may be sealed by painting over, or removed.

287 2021 $304,000

CIP-LMPS-11 Lake Michie Pumping Station Window Replacements

Project would repair Pumping Station and Elevator Penthouse windows. Project may replace windows in-kind, with windows which can be opened (aluminum sash windows), or with Kal-Wall translucent panels. Total window area approx. 2,300 SF.

287 2021 $138,000

CIP-LMPS-12 Lake Michie Pumping Station Ventilation System

Project would provide new ventilation/dehumidification system for Pumping Station. Project may include louvers and natural-gas make-up air units, approx. 15,000 CFM (3 air changes per hour), or may construct a pre-engineered, climate-controlled room within the Pumping Station building around electrical equipment only. Budget allowance reflects ventilation system for entire pump building; further evaluation required to determine alternative to be constructed

287 2021 $1,178,000

CIP-LMPS-13 Lake Michie Potable Water Supply & Septic System Rehabilitation

Project provides water supply (either new, dedicated water well or connection to existing well at caretaker's house) and wastewater service (septic tank) for the pumping station.

287 2019 $50,000

CIP-LMPS-14 Lake Michie Elevator Rehabilitation Project replaces elevator cab, winch, cabling and motor, at end of its expected service life 287 2022 $196,000

CIP-LMPS-15 Lake Michie Bridge Crane/Hoist System Improvements Project adds motor to replace hand chain drive, and other condition-related repairs 287 2022 $36,000

CIP-LMPS-16 Lake Michie Structural Concrete Repairs

Project performs targeted structural concrete repairs to patch spalling, cracks, seepage, holes in Pumping Station and Elevator Penthouse 282 2022 $25,000

CIP-LMPS-17 Lake Michie Pumping Station Asbestos Removal

Allowance for project to remove asbestos-containing material (office floor tiles) from Pumping Station office 144 2022 $5,000


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Fiscal Year

Total Budget ($)

Little River Pumping Station

CIP-LRPS-1 Little River Electrical Panel Replacements

Project replaces several electrical panels at end of their service lives, including power distribution panels, pull boxes, lighting panels and control panels 1777 2017 $16,000

CIP-LRPS-2 Little River Pump Inspections/Repairs Project provides contractor vibration inspection of Electrical Pumps, and repair as required; project also removes Raw Water Units 1 and 2 (Hydroturbine-Driven Pump and Driver) from service

1068 2017 $46,000

CIP-LRPS-3 Little River Emergency Generator Upgrade

Project provides 800 KW emergency generator capable of operating largest electrical pump and other Pumping Station facilities 1068 2017 $560,000

CIP-LRPS-4 Little River Electric Pump/Motor Replacements

Project replaces Electric Pumps/Motors at end of their service life. Raw Water Unit No. 4 will be replaced in-kind (capacity 30,000 gpm, Total Head 38 ft, 350 HP), and Raw Water Unit No. 3 will be increased to similar capacity to provided redundancy for Raw Water Unit No. 4 at future system water demand requirements.

712 2025 $1,463,000

CIP-LRPS-5 Little River Piping/Conduit Coatings Replacements

Allowance for project to replace coatings on exposed piping and conduit in Pumping Station 620 2019 $121,000

CIP-LRPS-6 Little River Thermal Destratification Compressor Project replaces existing thermal destratification system compressor 538 2017 $25,000

CIP-LRPS-7 Little River Roof Replacements (Pumping Station, Intake Structure, Stop Log Bldg)

Project would replace roofs for Little River Pumping Station, Intake Structure and Stop Log Building. City's standard roof design utilizes light-weight insulated concrete (LWIC) fill assembly with two-ply modified bitumen membrane roof, with new sheet-metal flashings and accessories. Roofs are 6,400 SF, 485 SF and 850 SF, respectively. City has selected a design consultant for the roof replacement.

287 2018 $364,000

CIP-LRPS-8 Little River Control Valve/Actuator Rehab (CV201, CV301, CV401)

Project would replace hydraulic actuators with electric actuators (Little River control valves CV201, CV301, CV401) 314 2021 $76,000

CIP-LRPS-9 Little River Structural Concrete Repairs

Project performs targeted structural concrete repairs to patch spalling, cracks, seepage, holes in Pumping Station, Intake Structure and Stop Log Building 144 2022 $75,000

CIP-LRPS-10 Little River Stop Log Bldg Re-painting Project paints Little River Stop Log Building exterior monorail to protect against continued corrosion 144 2022 $5,000

CIP-LRPS-11 Little River 54-inch Valve Installation Project installs a previously-procured 54-inch butterfly valve which in the Intake 54-inch line at the existing tee with 42-inch Pumping Station raw water line NA 2018 $125,000

CIP-LRPS-12 Little River Potable Water Supply Project provides water supply to Pump Building (either new, dedicated water well or connection to municipal water supply) NA 2019 $15,000


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Table 6-4. Lake Michie and Little River Dams Rehabilitation Plan Capital Improvement Project Descriptions


Fiscal Year

Total Budget ($)

Lake Michie Dam

CIP-LMD-1 Lake Michie Core Wall Investigation and Tree Removal

Confirm existence of the core wall and extend the access road to the gallery. The core wall appears to have been constructed based on original construction photos, but was not indicated on any available construction drawings. Remove trees from the left embankment. After removing the trees, restore grass vegetation to protect the embankment.

2459 2016 $75,000

CIP-LMD-2 Lake Michie Incremental Damage Analysis to Determine Design Storm

Perform an incremental damage analysis to determine the appropriate design storm. The results are likely to confirm that the embankment would need to be raised to prevent overtopping due to the increased design storm.

2459 2016 $20,000

CIP-LMD-3 Lake Michie Subsurface Investigation and Embankment Stability Analysis

There is no available geotechnical information on the embankment. Perform a subsurface investigation plan to evaluate embankment soils and foundation conditions, install piezometers, and replace Piezometer B-1. Perform a slope stability analysis using the results of the subsurface investigation.

2459 2016 $40,000

CIP-LMD-4 Lake Michie Embankment Filter – Design

Pending results of core wall investigation, design filter for seepage downstream of embankment. If the core wall is of sufficient quality and size to protect the embankment from seepage issues, the filter may not be necessary. If the core wall is inadequate, design a filter for the area with visible seepage at the downstream toe of the left embankment.

2459 2016 $15,000

CIP-LMD-5 Lake Michie Sluice Gates No. 1 and 2 Abandonment - Analysis

Gates are out of service/closed. 36" and 72" sluice gates submerged in sediment and debris and cannot be used to draw down the reservoir and are not compliant with state Dam Safety criteria. Perform a drain rate analysis to determine the drain rate to drawn down the reservoir potentially using 60" sluice gates in bays 1, 2, and/or 3 to satisfy state Dam Safety criteria. If acceptable, properly abandon this reservoir drain. Core from downstream face to see if conduit was abandoned. Create drawings and specifications to abandon the existing sluice gates and properly plug the reservoir outlet penetrations.

1686 2016 $60,000


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Fiscal Year

Total Budget ($)

Lake Michie Dam

CIP-LMD-6 Lake Michie Material Sampling and Testing and Piezometer Rehab

Core dam to obtain samples for testing. Evaluate concrete and foundation properties and lift line strengths. Install new piezometers and abandon old, which are unreliable. Sawcut gallery concrete across the joints in the floor and upstream wall to monitor potential relative structure movements.

2459 2017 $350,000

CIP-LMD-7 Lake Michie Concrete Monolith Grouting

Grout leaks at concrete monoliths. Leaks increase uplift pressures at the concrete lift lines, reducing the structural capacity of the joints. Design grouting program and drill vertical holes down from crest of the dam and fill with grout.

2459 2017 $210,000

CIP-LMD-8 Lake Michie Spillway Stability Rehab Analysis

Perform updated stability analyses and evaluate alternatives to address stability and deficiencies. Preliminary analyses indicated inadequate sliding stability at lift lines near the base. The void due to the gallery reduces strength and should also be investigated further. Design post-tensioned steel anchor system using results of the material sampling program. Anchors provide a downward compressive force that improves the sliding and overturning resistance. Determine the strand sizes, spacing, and required bond length to develop the anchor loads into the foundation material below the spillway. Based on preliminary analyses, it is anticipated that both the overflow and non-overflow sections will require anchors.

2459 2017 $280,000

CIP-LMD-9 Lake Michie Embankment Filter - Construction

Pending results of core wall investigation, install filter for seepage downstream of embankment.

2459 2017 $80,000

CIP-LMD-10 Lake Michie Trash Rack Bar Screen and Stop Log Replacement - Design

Design Intake screen replacement. Remove bar screen, and stop logs. Specify debris removal upstream. Design concrete repairs, new stop logs, and bar screen system.

2107 2017 $80,000

CIP-LMD-11 Lake Michie Right Concrete Tailrace Wall Investigation

No drawings are available for the tailrace walls. Perform an investigation to determine the construction of the undermined tailrace walls and design a repair for the areas that are undermined.

983 2017 $40,000

CIP-LMD-12 Lake Michie Gallery Inflow Monitoring Monitor and record gallery inflows on monthly basis. Design and install weirs in gutter with staff gage to record water level. This activity depends on whether or not the drains function.

938 2017 $35,000


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Fiscal Year

Total Budget ($)

Lake Michie Dam

CIP-LMD-13 Lake Michie Spillway Apron Repairs - Design

Perform a scour analysis and design repairs to spillway apron. The spillway apron has scoured and been undercut below the concrete spillway several feet in some areas. Design armoring of the spillway apron to improve overtopping protection and protect against continued scour.

938 2017 $65,000

CIP-LMD-14 Lake Michie Trash Rack Bar Screen and Stop Log Replacement - Construction

Install Intake screen replacement. Remove bar screen, and stop logs. Remove debris upstream. Perform concrete repairs, install new stop logs, and install bar screen system.

2107 2018 $465,000

CIP-LMD-15 Lake Michie Decommission Trash Rake

Decommission existing trash rake, which is not functional and not necessary. Perform this work in combination with sluice gate replacement. Remove and discard the trash rake.

2107 2018 $45,000

CIP-LMD-16 Lake Michie Intake Sluice Gate Replacements - Design

Design gate replacements to replace six 12", and three 42" Sluice Gates with manual actuators. Potential cost reduction if study shows some of these gates can be properly abandoned. Rehab one 60-inch gate for low level outlet. Abandon remaining two 60-inch gates.

1692 2018 $160,000

CIP-LMD-17 Lake Michie Sluice Gates No. 1 and 2 Abandonment - Construction

Permanently abandon 72" and 36" intake sluice gates. These gates are submerged below sediment and debris and have been out of service for years. The gate stems are in poor condition. The penetrations for the gates were plugged when inspected at the downstream face. It is not clear whether the plug was designed to resist full hydrostatic pressure from the reservoir if the gates are removed. Gates may not be necessary pending results of drain study. Abandonment would consist of abandoning the gates and filling the conduits with grout from the downstream end. This project may not be needed if investigations indicate that conduits were grouted previously.

1686 2018 $150,000

CIP-LMD-18 Lake Michie General Concrete Repairs - Design

Design concrete repairs. Initial round addresses training walls and more extensive repairs (e.g. repairs requiring sawcutting, formwork, temperature/shrinkage reinforcement, or steel dowels at areas of large amounts of spalling, cracking, or weathering) to the facing of the spillway. Downstream concrete lift lines have areas of significant spalling.

938 2018 $140,000


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Fiscal Year

Total Budget ($)

Lake Michie Dam

CIP-LMD-19 Lake Michie Spillway Capacity Improvements - Design

Evaluate spillway capacity needs and address. Perform engineering evaluation of alternatives to address potential embankment raise and armoring below the non-overflow area.

2459 2019 $225,000

CIP-LMD-20 Lake Michie Post-Tensioned Anchor Installation

Install post-tensioned anchors. Drill down from the crest of the spillway into the rock foundation and install double corrosion protected post-tensioned steel strand anchors. Grout solid the annular space around the anchors. Prerequisite projects are to perform material testing and perform revised stability analysis.

2459 2019 $2,500,000

CIP-LMD-21 Lake Michie Right Concrete Tailrace Wall Repair

Repair undermined wall. It is expected that this will require construction of a cofferdam, excavation down to sound foundation material, placement of concrete under the existing concrete, and sloping the concrete down towards the center of the tailrace to protect against undercutting of the repair concrete. Depending on the results of the investigation, temporary shoring of the wall may be required during construction.

983 2019 $350,000

CIP-LMD-22 Lake Michie General Concrete Repairs - Construction

Initial round of concrete repairs including training walls. Restore significantly spalled areas. For large repair areas, dowel in rebar to enhance the bond of the repair concrete to the existing. For smaller spalls, clean and patch.

938 2019 $1,200,000

CIP-LMD-23 Lake Michie Spillway Capacity Improvements - Construction

Construction cost assumes that the embankment needs to be raised 5 ft and the embankment armored below the non-overflow area.

2459 2020 $2,300,000

CIP-LMD-24 Lake Michie Intake Sluice Gate Replacements - Construction

Replace six 12", and three 42" Sluice Gates with manual actuators. Potential cost reduction if study shows some of these gates can be properly abandoned. Rehab one 60-inch gate for low level outlet. Abandon remaining two 60-inch gates. Prerequisite project is to design sluice gate replacements.

1692 2020 $1,100,000

CIP-LMD-25 Lake Michie Spillway Apron Repairs - Construction

Clean foundation and install dental concrete and mass concrete downstream of spillway at apron. Prerequisite projects are to determine new IDF and design spillway apron repairs.

938 2020 $650,000


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Fiscal Year

Total Budget ($)

Lake Michie Dam

CIP-LMD-26 Lake Michie SCADA and Security System

Add automatic Supervisory Control and Data Acquisition (SCADA) at instrumentation. SCADA provides the ability to capture and transmit data in real-time to remote office to make management decisions on control of dam assets. Add security camera system and alarm system.

699 2020 $140,000

CIP-LMD-27 Lake Michie Bathymetry and Study of Sedimentation

Perform bathymetry to track the deposition of sediment in the reservoir. Perform study of sedimentation to identify impact on water quality and water storage capacity.

135 2024 $20,000

CIP-LMD-28 Lake Michie Removal of Sediment

Remove sediment from reservoir to avoid adverse impacts on water quality and water storage/supply. Cost assumes sediment removal in vicinity of reservoir drains only and may increase significantly (to multi-million $ project) if reservoir capacity must be increased, which depends on the results of the CIP-LMD-27 study.

135 2024 $100,000

CIP-LMD-29 Lake Michie Road Resurfacing Improve/resurface roadway. Existing gravel road is in good shape now, but will likely need maintenance later in the 10-year CIP due to normal deterioration.

135 2025 $75,000


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Fiscal Year

Total Budget ($)

Little River Dam

CIP-LRD-1 Little River Concrete Drainage Ditch Repair

Design and repair for undermined and collapsed portion of concrete drainage ditch at left embankment. The concrete ditch has dropped over one foot in places, buckled, and is eroding embankment material.

2390 2016 $85,000

CIP-LRD-2 Little River Spillway Gate Operator Replacement

Replace actuators which are over 30 years old. Actuators at gate no. 1, 2, 6, and 9 are currently functional but beyond intended service life. No. 5, 7, and 8 are not currently functional and need to be operational to safely pass large design storms. Cost estimates are based on Auma products. Potentially install new conduit and wiring to the actuators and capping the existing conduit for the current actuators.

2000 2016 $210,000

CIP-LRD-3 Little River Embankment Seepage and Stability Analysis

Perform a transient seepage analysis and update rapid drawdown stability model to verify if stability factor of safety can be improved to meet state Dam Safety requirements given existing conditions.

425 2016 $7,500

CIP-LRD-4 Little River Inundation Zone Analysis

Analyze inundation zone upstream of dam for design storm. Assets upstream of dam may be inundated (e.g. bridge overtopping) and may need to be considered in gate operations and an updated Emergency Action Plan. No remedial work on any assets is included in this task.

116 2016 $5,000

CIP-LRD-5 Little River Emergency Action Plan Update

Update the Emergency Action Plan (EAP), which was last updated in January 2012. Emergency Action Plans are required to be updated on an annual basis. Major rehab projects affecting the EAP should include provisions for updating the EAP.

116 2016 $15,000

CIP-LRD-6

Little River Left Spillway Approach Wing Wall, Piezometers, Right Spillway Training Wall Survey Monuments, and Survey Monitoring Points SM-1 Thru SM-6

Check total depths of piezometers and compare to as-built depths to determine whether sediment build-up is causing invalid water level readings, record clogged piezometers, and develop a plan of action for when threshold levels are exceeded. Add 2 survey monuments along top of wall between points 7C and 7D and survey on an annual basis to identify future movement of top of wall, survey cost included with survey monitoring. Perform annual survey of SM-1 through SM-6, survey points on structures including spillway, retaining wall near the tunnel outlet, and the lower right spillway training wall. Surveyor to monitor left inlet wing wall for movement within inspection contract. Add survey monuments as part of CIP.

983 2018 $45,700


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Fiscal Year

Total Budget ($)

Little River Dam

CIP-LRD-7 Little River Left Spillway Sidewall Repairs

Remove and replace existing sealant at contraction joints in spillway sidewalls. Perform miscellaneous concrete repairs. Repair cracked grouted riprap.

983 2018 $50,000

CIP-LRD-8 Little River Vegetation Removal at Saddle Dam

Clear vegetation at saddle dam. There are several houses constructed very close to the saddle dam. The trees on the saddle dam need to be removed and the holes filled with embankment material and protected against erosion.

425 2018 $20,000

CIP-LRD-9 Little River Survey Monitoring Perform annual survey of SM-1 through SM-6, survey points on structures including spillway, retaining wall near the tunnel outlet, and the lower right spillway training wall.

350 2018 $4,000

CIP-LRD-10 Little River Tunnel Repairs

Prepare profile drawing along tunnel alignment showing joint location where leakage occurs. Design, install new lights, and provide construction administration. Evacuate standing water and sediment in diversion tunnel and clean joints so that seepage locations and accumulation of new sediment can be easily observed. Add stationing numbers and joint numbers in tunnel to facilitate monitoring of the leakage.

911 2020 $141,000

CIP-LRD-11 Little River SCADA and Security System

Add automatic Supervisory Control and Data Acquisition (SCADA) at instrumentation. SCADA provides the ability to capture and transmit data in real-time to remote office to make management decisions on control of dam assets. Trespassers have been spotted on the dam. Add security camera system and alarm system.

418 2020 $100,000

CIP-LRD-12 Little River Upstream Slope Erosion Protection

Replace deteriorated Fabriform erosion protection with riprap. Fabriform is showing signs of aging, but is not yet compromising the stability of the embankment.

425 2021 $300,000

CIP-LRD-13 Little River Road Resurfacing Improve/resurface roadway. Asphalt concrete road is currently in good shape, with some cracks and differential settlement at the spillway.

142 2025 $100,000


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6.5 Little River Dam Rehab Summary

Schnabel identified 13 asset deficiency recommendations in the 10-year CIP and 11 recurring activities planned within the 50-year planning horizon. The highest risk issues should be addressed first. These include the undermined portion of the concrete drainage ditch at the left embankment and the replacing the spillway gate operators.

Some of the other large activities included in the 10-year CIP are rehabbing the diversion tunnel to observe seepage, replacing the deteriorated Fabriform erosion protection, adding an automatic SCADA and security system, and resurfacing the road.

Some of the major recurring activities are general concrete repairs, cleaning out the riprap, and maintaining underwater assets by water-jet cleaning and dredging.

6.6 Lake Michie Dam Rehab Summary

Schnabel identified 29 asset deficiency recommendations in the 10-year CIP and 11 recurring activities within the 50-year planning horizon. At Lake Michie, the Dam Safety issues should be addressed first. Based on our observations and preliminary calculations, the dam does not appear to be in danger of imminent collapse for normal conditions. However, all Dam Safety issues must be resolved before the dam will be compliant with Dam Safety and considered safe for the more extreme events for which it is required to withstand.

The major Dam Safety issues are confirming the embankment core wall, determining the current design storm and spillway capacity needs, performing a subsurface investigation to evaluate embankment soils and foundation conditions, installing post-tensioned anchors to address stability deficiencies, repairing the spillway apron, and rehabbing the sluice gates for reservoir drainage needs. Some of the other major activities included in the 10-year CIP are initial concrete repairs to the spillway, adding an automatic SCADA and security system, and repairing the undermined right tailrace walls.

Some of the major recurring activities are general concrete repairs, cleaning out the riprap, and maintaining underwater assets by water-jet cleaning and dredging.

6.7 Little River Pumping Station Rehab Summary

BC identified 12 projects to address asset deficiencies in the 10-year CIP or through operations & maintenance (O&M) projects during the same period, and 90 recurring asset rehabilitation and replacement (R&R) activities to be planned within the 50-year planning horizon. At Little River, projects related to safety, level of service (capacity and redundancy) or emergency operation should be prioritized.

Service Life Related Asset Replacements: The Little River Pumping Station is in generally good condition, but as the facility nears 30 years in service, many of the mechanical and electrical assets will soon be nearing the end of their expected service life. The primary condition issues observed are deterioration of equipment which has not been used (e.g., hydro-turbine driven pump, mechanical rake); thermal destratification system compressor failures; obsolete hydraulic actuators for key pump station valves; areas of poor concrete condition; fair/poor roof condition; and a few areas of deteriorated electrical panels and wiring. Observed condition issues will be addressed through capital projects or work orders, including prioritized projects to replace deteriorated/obsolete electrical panels (LRPS-1),


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investigate and correct Raw Water Unit No. 4 (Two-Speed Electric Motor-driven Brown Pump) vibration issues (LRPS-2); replace coatings on piping, conduit, valves and targeted exterior structures (LRPS-5 and LRPS-10); repair the thermal destratification system (LRPS-6); replace building roofs (LRPS-7); and make structural concrete repairs (LRPS-9). These projects will maintain existing function and capacity.

In addition, proposed project LRPS-12 provides a potable water supply to the pump building, either by a new water well or connection to municipal water supply.

Throughout the planning horizon, the major recurring R&R activities will include scheduled rehabilitation and replacement of pumps, valves, roofs, other mechanical equipment; and electrical gear and wiring at the end of their service lives; pump/motor rebuilds; periodic testing of electrical equipment; concrete repairs; and replacement of coatings for walls and piping. The planning interval for these long-term R&R projects is discussed further in Section 6.9.

Reliability and Redundancy: Two of the recommended CIP projects for Little River (LRPS-3 and LRPS-4) enhance redundancy of function for the raw water pumping station through (1) an emergency generator capable of running the electrical pumps, dam and intake facilities, and other electrical demands when utility power is interrupted; and (2) replacing the electric pumps and motors so that both Raw Water Units are capable of 30,000 gpm capacity. Currently, only Raw Water Unit No. 4 has this capacity, which is approximately equal to the upgraded Brown WTP capacity. Having both pumps at this capacity will provide additional operational flexibility for the raw water pumping station since either pump could be used to meet peak day needs, and in combination with the generator will allow the City to mothball the hydroturbine-driven pump and driver (LRPS-2). The proposed projects also include electrical upgrades and soft starts for the pumps and destratifier to address inrush current issues with the current electrical design which would otherwise require a larger (1 MW or more) generator size. The proposed 800 KW generator would be sized to operate one pump at the future capacity.

Valves and Actuators: The hydraulic-actuated valves at both Little River and Lake Michie facilities are an obsolete technology which is prone to leaks and maintenance-intensive. Recommended CIP project LRPS-8 replaces current hydraulic actuators at three control valves with electric actuators. In addition, the CIP includes a project (LRPS-11) to install a previously-purchased 54-inch butterfly valve in the intake building raw water line just upstream of the tee with the 42-inch pumping station raw water line.

6.8 Lake Michie Pumping Station Rehab Summary

BC identified 17 projects to address asset deficiencies in the 10-year CIP or through operations & maintenance (O&M) projects during the same period, and 74 recurring asset rehabilitation and replacement (R&R) activities to be planned within the 50-year planning horizon. At Lake Michie, projects related to safety, level of service (capacity and redundancy) or emergency operation should be prioritized.

Reliability and Redundancy: Four of the recommended CIP projects for Lake Michie (LMPS-1, LMPS-2, LMPS-3 and LMPS-6) enhance safety and redundancy of function for the raw water pumping station through (1) replacement of the obsolete medium voltage electrical equipment (switchgear, transfer switch, motor control centers); (2) upgrading the incoming electrical feed from Duke Energy; (3) installing a 1.5 MW emergency generator capable of running the electrical pumps, dam and intake facilities, and other electrical demands when utility power is interrupted; and (4) replacing the electric pumps and motors so that both electrical pumps are capable of at least the current 20,833 gpm capacity of Electric Pump No. 1, or increased to 30,000 gpm capacity, which will meet the future upgraded Brown WTP treatment capacity.


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Currently, neither electrical pump has this capacity. Having both pumps at 30,000 gpm capacity will provide additional operational flexibility for the raw water pumping station since either pump could be used to meet peak day needs, and in combination with the generator will allow the City to mothball the hydroturbine-driven pumps. The proposed projects also include upgrades to electrical facilities sufficient to accommodate the much larger pumps. The proposed generator would be sized to operate one pump at the future capacity.

Note that a 50-percent increase in pump capacity, to 30,000 gpm for each electric pump, would be projected to result in pipe velocities of 7 ft/sec in the twin 30-inch raw water transmission lines between the pumping station and the old Flat River Pumping Station where lines change to 42-inch and 24-inch for the remainder of the route to Brown WTP. The higher velocity has pump design and pipe surge implications which should be considered and may result in additional capital improvement requirements in the raw water transmission system.

Service-Life Related Asset Replacements: The Lake Michie Pumping Station is in generally fair condition though showing its age (90 years), with a number of wear-related issues and equipment failures demand attention in the near term. The primary condition issues observed are pump wear and redundancy, including one of the two hydroturbine-driven pumps unable to operate; deterioration of the medium voltage electrical equipment; obsolete hydraulic actuators for key pump station valves; areas of poor concrete condition; fair/poor roof condition; and lack of ventilation/humidity control in the pump building.

Observed condition issues will be addressed through capital projects or work orders, including prioritized projects to replace deteriorated/obsolete electrical panels (incorporated as part of the LMPS-2 electrical equipment replacements project); replace the thermal destratification system (LMPS-5); replace coatings on piping, conduit and valves (LMPS-7); inspects piping and conduit for corrosion, and replaces these as indicated by the inspections (LMPS-8), replace building roofs (LMPS-7); make structural concrete repairs (LMPS-9); repaint the pumping station interior, abating for existing lead-based paint (LMPS-10); renovate or replace the existing elevator (LMPS-14); and make structural concrete repairs (LMPS-16). These projects will maintain existing function and capacity.

Throughout the planning horizon, the major recurring R&R activities will include scheduled replacement of pumps, valves, roofs, other mechanical equipment; and electrical gear and wiring at the end of their service lives; pump/motor rebuilds; periodic testing of electrical equipment; concrete repairs; and replacement of coatings for walls and piping. The planning interval for these long-term R&R projects is discussed further in Section 6.9.

Valves and Actuators: Recommended CIP project LMPS-4 replaces current hydraulic actuators at pumping station control valves with electric actuators, as well as service-life related replacements and repairs for a number of other valves and actuators.

Pump Building Improvements and Renovations: Several CIP projects are targeted to pump building renovations or improvements. Proposed projects LMPS-11 and LMPS-12 address current deficiencies in the building ventilation system, which impacts the condition of the electrical gear located next to the electrical pumps as well as the painted walls, through window replacements and addition of a ventilation / dehumidification system. A number of options are available to the City to address this need, ranging from


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a system serving the entire building to construction of an air-conditioned, pre-engineered room enclosing only the electrical equipment.

Restoration of a potable water supply and wastewater (septic tank) service for the pump building is also recommended (LMPS-13). A motor for the bridge crane hoist system would replace the current hand chain (LMPS-15). Finally, proposed project LMPS-17 removes small quantities of asbestos-containing floor tiles from the pumping station office.

6.9 50-Year Rehabilitation Plan

Once the proposed work to address current, observed deficiencies is completed, the City should anticipate and budget for ongoing renewal and replacement work for dam and raw water pumping station facilities and assets to maintain the desired level of service. Within the next 50 years, to the 2065 planning horizon, Lake Michie and Little River dams and raw water pumping stations will require major rehabilitation projects as well as asset replacements.

Lake Michie and Little River dams require a large amount of rehabilitative work in the first few years to address state Dam Safety deficiencies. After these issues are addressed, there are still routine maintenance and replacement needs in the remainder of the 50-year planning horizon, but these needs are not as numerous or costly as for the pumping station.

Table 6-5 summarizes the types and frequency of anticipated asset renewal and replacement projects which are expected to be required for assets at Lake Michie and Little River raw water pumping stations during the next 50 years. Recommendations for specific asset renewal and replacement projects for the pumping stations, including project year and anticipated cost (in 2015 $) are included in Appendix I. Recommendations for the dams are included in Appendix J.


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Table 6-5. Types of Recommended Renewal & Replacement Activities, Lake Michie/Little River Raw Water Pumping Stations

Renewal Activity Asset Type Rehabilitation/Replacement Frequency (Years)

Replacement Piping (DIP, PVC) 100

Replacement Civil Assets (e.g., Roads, Drainage, Fencing) 75

Replacement Building-Structure 60

Replacement Pumps 40

Replacement Motors 40

Replacement Valves 40

Replacement Electrical Conduit & Wiring 40

Replacement Compressors 30

Replacement Other Mechanical Equipment 30-50

Replacement Electrical Equipment 30

Replacement Emergency Generators 30

Replacement Site Lighting 30

Replacement Instrumentation/Meters 15

Rehab-Rewind Motors Motors 20

Rehab-Rewind Motors, Major Maintenance Emergency Generator 15

Rehab-Mods and Minor Replacements Piping, Electrical Conduit & Wiring 15

Rehab-Bearings/Seals/ Major Maintenance

Pumps, Compressors, Oil Accumulator System, Other Mechanical Equipment 10

Rehab-Repairs Following Inspection

Compressors, Other Mechanical Equipment, Bridge Cranes, Elevator, Overhead Doors, Water Well 10

Rehab-Outside Vendor Tests Major Electrical Equipment 10

Maintenance-Pump Out Septic Tank 10

Rehab-Concrete Repair Building-Structure 8


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Table 6-6. Types of Recommended Renewal & Replacement Activities, Lake Michie/Little River Dams

Renewal Activity Asset Type Rehabilitation/Replacement Frequency (Years)

Replacement – Gate Operators Spillway Gate Operators 30

Replacement – Log Boom Reservoir 15

Rehab – Clean Out Riprap Riprap 15

Rehab-Tree Removal Left Abutment 10

Rehab-Concrete Repair Concrete Structures - All 10

Rehab – Underwater Survey and Dredging Reservoir 10

Rehab – Clean Gates, Stems, Bar Screens, Stop Log Slots Riser Sluice Gates, Bar Screens 10

Rehab – Update Emergency Action Plan Reservoir 1

Rehab - Survey Survey Monuments 1

Figure 6-3 illustrates recommended capital and O&M expenditures for the 10-year period FY2016-2025. Figure 6-4 illustrates the total capital, O&M, and renewal and replacement expenditures recommended for the 10-year period FY2016-2025.

The renewal and replacement expenditures over the 50-year period FY2016 to FY2065, including the initial 10-year period detailed above and specific asset replacements and civil/mechanical/electrical/instrumentation rehabilitation projects following the guidance of Table 6-5 and Table 6-6. Figure 6-5 shows total capital projects and renewal and replacement expenditures predicted over the 50-year period 2016-2065 organized by facility. The total cost is approximately $50 million. The City should be prepared to fund asset replacements or substantial rehabilitation as the equipment and facilities age and reach the expected end of their service lives.


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Figure 6-3. Preliminary Estimate of Durham Dam & Raw Water Pumping Station Capital Improvement Plan for 10-Year Interval 2016-2025

Figure 6-4. Preliminary Estimate of Durham Dam & Raw Water Pumping Station Capital Improvement Plan + R&R Projects for 10-Year Interval 2016-2025


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Figure 6-5. Preliminary Estimates of City of Durham Long-Range Dam Pumping Station Renewal

and Replacement Expenditures over 50 Year Interval 2016-2065, by Facility

Because projection of long-range asset renewal and replacement activities rely on asset life span as well as observed condition, the funding requirements in Figure 6-5 include spikes representing renewal similar assets installed at the same time. If desired to achieve a more uniform funding level over the planning horizon, the funding plan shown in Figure 6-5 could be leveled to an extent by moving rehabilitation projects forward or back. In addition, the 10-year capital plan for renewal activities could sequence project execution to address funding spikes, with the exception of the Dam Safety activities, which do not meet regulatory requirements and create added risk to the City until addressed.


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CONDITION ASSESSMENT AND REHABILITATION PLAN

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