Cost Trends and Estimates for Dam

Rehabilitation in the Commonwealth of

Virginia

Stefany A. Baron

Thesis submitted to the faculty of the Virginia Polytechnic Institute and State University in partial

fulfillment of the requirements for the degree of

Master of Science in

Civil Engineering

Randel L. Dymond, Chair Kevin D. Young

Clayton C. Hodges

May 18, 2020 Blacksburg, Virginia

Keywords: dam safety, dam rehabilitation, dam removal, cost estimating

Cost Trends and Estimates for Dam Rehabilitation in the Commonwealth of Virginia

Stefany Baron

Academic Abstract

In recent years, the United States has seen a high demand for dam rehabilitation projects

as most dam infrastructure has started to reach or exceed the expected life span of 50-70 years.

Rehabilitation projects can be very expensive, however, and the funding options for dam owners

are limited. To raise awareness, organizations such as ASDSO and the Virginia DCR release cost

estimates every few years to encourage more investment in dam infrastructure. Unfortunately,

many cost estimates have been made with limited data and outdated methodologies. This research

collects a new sample of cost data for Virginia dam rehabilitation projects and uses it to assess key

factors for cost estimating. Factors such as height, drainage area, hazard classification, and

ownership type were used to make regression models that predict the cost of addressing Virginia’s

non-compliant dams. This study estimates that approximately $300 million is needed to address

Virginia’s 98 deficient high hazard, local government owned dams and that $122 million of that

estimate is need for SWCD dams alone.

Cost Trends and Estimates for Dam Rehabilitation in the Commonwealth of Virginia

Stefany Baron

General Audience Abstract

Dam rehabilitation refers to the repair, removal, or upgrade of an existing dam structure.

Rehabilitation projects are done when dams start to exceed their intended life span (approximately

50-60 years) or when policy makers change the required safety standards. The demand for dam

rehabilitation has been increasing for the past several years as more and more dams are being

identified as unsafe, but the available funding for rehabilitation projects is limited and competitive

to obtain for dam owners. To raise awareness, dam safety agencies release cost estimates every

few years to encourage government leaders and the general public to take action. However, these

estimates need to be taken with caution as they are often made with limited data availability and

outdated methodologies. This research collects a new sample of cost data for Virginia dam

rehabilitation projects that have occurred in the last 15 years. Dam characteristics such as height,

watershed size, downstream risk potential, and ownership type were used to form equations that

predict the cost of addressing Virginia’s non-compliant dams. This study estimates that

approximately $300 million is needed to address Virginia’s 98 deficient high hazard, local

government owned dams and that $122 million of that estimate is need for Virginia’s Soil and

Water Conservation District dams alone.

iv

Acknowledgements

First, I would like to thank my committee, Dr. Randy Dymond, Kevin Young, and Dr. Clay Hodges

for their help and guidance throughout this research process. I have greatly appreciated all their

time and feedback during our committee meetings.

I would like to thank James Martin and Charles Wilson from the Virginia DCR for not only

providing me with a lot of data (and access to the DSIS) but for also taking the time to answer all

my questions about DCR funding, certificates, and Virginia dam safety standards through our

many phone calls and emails.

Thank you to Mark Ogden, John Ritchey, and Rex Holmlin who have worked for the ASCE Report

Card and ASDSO cost estimating committees. Thanks for taking the time to speak with me about

how estimates have been made and how the ASDSO operates. I am grateful for their honesty and

for their words of encouragement to continue “my detective work”.

A big thank you to all the private dam owners that took the time to give me the data I needed and

were willing to share information on their dam rehabilitation experiences. Many private dam

owners shared their personal stories and frustrations about the dam rehabilitation process with me.

Although I did not include this information in my thesis, I will take these stories with me when I

go into the dam engineering industry after graduation and do my best to make things better in

whatever way I can.

Thanks to my friends in 310 Patton for all the jokes, memes, and small distractions. There was

rarely a boring day in the office, and I have missed all of you greatly during this pandemic

lockdown. I hope our paths can cross again when the world is safer and healthier.

Thank you Dylan for being my best friend at Virginia Tech since day one and for being there for

every single happy and frustrating moment of grad school. I could not have asked for a better co-

TA, classmate, or thesis writing buddy.

Lastly, the most important thank you goes to my incredible parents who have sacrificed so much

for me to be where I am today. Their never-ending and unconditional support has meant the world

to me. Nada de esto sería posible sin ustedes. ¡¡Los quiero MUCHO!!

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Table of Contents

Academic Abstract .......................................................................................................................... ii

General Audience Abstract ............................................................................................................ iii

Acknowledgements ........................................................................................................................ iv

Table of Contents ............................................................................................................................ v

List of Figures ............................................................................................................................... vii

List of Tables ............................................................................................................................... viii

List of Abbreviations and Acronyms ............................................................................................. ix

Chapter 1 Introduction .................................................................................................................... 1

1.1 Background ........................................................................................................................... 1

1.2 Problem Statement ................................................................................................................ 2

1.3 Purpose and Objectives ......................................................................................................... 3

Chapter 2 Literature Review ........................................................................................................... 5

2.1 History of Dams in the United States .................................................................................... 5

2.2 Virginia Standards for Dam Safety Compliance ................................................................... 6

2.2.1 Hazard Classifications and Design Criteria .................................................................... 6

2.2.2 Hazard Creep and Reclassification of Dams .................................................................. 8

2.2.3 Changes to PMP Values in 2016 .................................................................................... 9

2.3 Enforcing Dam Safety ......................................................................................................... 10

2.4 Rehabilitation Options for Dams......................................................................................... 10

2.4.1 Spillway Design Flood Upgrade Projects ..................................................................... 11

2.4.2 Other Upgrades ............................................................................................................. 11

2.4.3 The Environmentalist Movement Towards Dam Removal .......................................... 12

2.5 Funding Assistance and Grant Programs for Dam Rehabilitation ...................................... 13

2.5.1 USDA Natural Resources Conservation Services Funding for Dams .......................... 13

2.5.2 WIIN Federal Funding for Dams.................................................................................. 13

2.5.3 DCR Funding for Dams ................................................................................................ 14

2.5.4 Miscellaneous Grants ................................................................................................... 14

2.6 The Cost and Risk of Not Upgrading a Dam ...................................................................... 15

vi

2.7 Previous Cost Estimating Studies and Reports ................................................................... 16

2.7.1 Cost Estimates from ASDSO ....................................................................................... 16

2.7.2 Cost Estimates from the DCR in 2011 ......................................................................... 17

2.7.3 Cost Estimates from the DCR in 2018 ......................................................................... 18

2.8 Summary ............................................................................................................................. 18

Chapter 3 Cost Trends and Estimates for Dam Rehabilitation in the Commonwealth of Virginia

....................................................................................................................................................... 20

3.1 Introduction ......................................................................................................................... 20

3.2 Data Collection .................................................................................................................... 23

3.3 Analysis Methods ................................................................................................................ 24

3.3.1 Consideration for Inflation ........................................................................................... 24

3.3.2 Continuous Factors vs. Cost ......................................................................................... 25

3.3.3 Categorical Factors vs. Cost ......................................................................................... 27

3.3.4 Continuous Factors vs. Cost Separated by Category .................................................... 28

3.3.5 Theil Sen Regression Analysis ..................................................................................... 30

3.4 Predictions of Future Costs ................................................................................................. 33

3.5 Evaluating Estimates made by the VA DCR ...................................................................... 34

3.6 Discussion and Conclusions ................................................................................................ 35

Chapter 4 Conclusion .................................................................................................................... 37

4.1 Implications ......................................................................................................................... 37

4.2 Future Work ........................................................................................................................ 38

References ..................................................................................................................................... 39

Appendix A – Survey Questions................................................................................................... 42

Appendix B – Sample of Dam Database ...................................................................................... 43

Appendix C –Spearman’s Rho Equations and R Code ................................................................. 44

Appendix D – R Code Theil Sen Regression Models................................................................... 45

vii

List of Figures

Figure 2-1 Components of a Typical Earthen Dam (FEMA P-911 2016) ................................... 11

Figure 3-1 Mean and median ages of dams in Virginia categorized by ownership type (NID

2018). ............................................................................................................................................ 20

Figure 3-2 Certificates granted by the DCR as of February 2020 (DSIS 2020). ......................... 21

Figure 3-3 Responses from the contacted dams. .......................................................................... 24

Figure 3-4 Normalized historical cost index values..................................................................... 25

Figure 3-5 Distribution of rehabilitation project costs (n = 60). .................................................. 26

Figure 3-6 Continuous Factors vs. Total Rehabilitation Project Cost (n = 60). .......................... 26

Figure 3-7 Box and whisker plots for the collected data holistically and for the collected data

separated into categories. .............................................................................................................. 28

Figure 3-8 Models 2 (A/B), 3(C/D), 5(E/F), and 7(G/H) with and without outliers. .................. 32

viii

List of Tables

Table 1.1 ASCE Report Card Grades (ASCE 2017) ...................................................................... 1

Table 1.2 ASDSO repair cost estimates for all dams in the U.S. regardless of Hazard Class

(ASDSO 2019) ................................................................................................................................ 2

Table 1.3 Virginia DCR grant program awards to local government and privately owned dams . 3

Table 2.1 Hazard Classification Descriptions (DCR 2020c). ........................................................ 7

Table 2.2 Impounding Structure Regulations for Virginia as of 2008 (4VAC50-20-40) .............. 8

Table 2.3 Impounding Structure Regulations for Virginia Prior to 2008 (4VAC50-20-50).......... 8

Table 2.4 DCR Dam Safety and Floodplain Management Grants for 2017-2019 (DCR 2020b). 14

Table 2.5 Total Cost Estimates from the 2011 DCR Report for Virginia Significant and High

Hazard Dams ................................................................................................................................. 18

Table 3.1 Previous Cost Estimates for Virginia Dam Rehabilitations (DCR 2011, ASDSO 2019,

DCR 2018) .................................................................................................................................... 22

Table 3.2 Results from the Spearman’s Rho Hypothesis Test for Continuous Factors vs. Cost. 27

Table 3.3 Correlation Analysis for Numerical Factors vs. Cost for Dams Separated by Category.

....................................................................................................................................................... 29

Table 3.4 Theil Sen regression models for all combinations with a valid rho correlation........... 31

Table 3.5 Tabulated cost estimate results for one high hazard and local government owned dam

that is 65 feet tall and has a drainage area of 8 mi2. ...................................................................... 33

Table 3.6 Comparison of DCR’s 2011 estimates against actual project costs and against Theil

Sen estimates. The data is ranked by the DCR’s percent error. .................................................... 34

Table 3.7 Cost estimates of rehabilitating Virginia SWCD dams that need repair (DCR 2018) . 35

ix

List of Abbreviations and Acronyms

ACBs - Articulating Concrete Blocks

ASCE - American Society of Civil Engineers

ASDSO - Association of State Dam Safety Officials

ASW - Auxiliary Spillway

CCT - Bureau of Reclamation’s Construction Cost Trends

DCR - Virginia Department of Conservation and Recreation

DSIS - Dam Safety Inventory System

EAP - Emergency Action Plan

ENR - Engineering New Record

EPA - Environmental Protection Agency

FEMA - Federal Emergency Management Agency

NGO - Non-Governmental Organization

NOAA - National Oceanic and Atmospheric Administration

NRCS - Natural Resource Conservation District

O&M - Operation and Maintenance

PMF - Probable Maximum Flood

PMP - Probable Maximum Precipitation

RCC - Roller Compacted Concrete

SWCD - Soil and Water Conservation District

VAC - Virginia Administrative Code

VRA - Virginia Resource Authority

USACE - United States Army Corps of Engineers

USDA - United States Department of Agriculture

USFWS - United States Fish and Wildlife Services

WIIN - Water Infrastructure Improvements for the Nation Act

1

Chapter 1 Introduction

1.1 Background

Safe infrastructure plays an important role in the productivity and quality of life of a

society. To evaluate the infrastructure condition in the United States, the American Society of Civil

Engineers (ASCE) releases an Infrastructure Report Card every four years with the A-F scale

shown in Table 1.1. ASCE uses these report cards to educate and inform both the general public

and government leaders about the importance of investing in America’s infrastructure (ASCE

2017).

Table 1.1 ASCE Report Card Grades (ASCE 2017)

The ASCE Report Card assesses 16 categories of infrastructure including bridges, roads,

energy, and wastewater. Dam infrastructure is one of the 16 categories graded by the ASCE and it

is the category that is investigated in this research. Dams have been altering America’s waterways

for centuries to provide people with drinking water, irrigation, hydropower, and recreation. The

failure of a dam can be a catastrophic event with long lasting crippling effects to the surrounding

communities (Ellingwood et al. 1993). The 2017 ASCE Report Card gave dams a D grade at the

national level and a C grade in the state of Virginia. Although Virginia is currently outperforming

many states in dam infrastructure and dam safety, there is still much room for improvement. The

state has been actively restructuring their dam safety regulations and funding programs over the

last two decades, but they are still not meeting the needs of all dams and dam owners. Only 302

(11%) of Virginia’s 2,790 dams meet full operational and maintenance requirements. 384 dams

(14%) have been identified as needing rehabilitation within the next two years. Over 1,900 dams

(75%) need proper inspections and assessments to determine if standards are being met. The

ASCE Report Card grade of Virginia dams will not improve until more dams have been inspected

2

and rehabilitated. The challenge with dam rehabilitation, however, is that projects are expensive,

and funding is limited and competitive.

1.2 Problem Statement

The Virginia Department of Conservation and Recreation (DCR) and the Association of

State Dam Safety Officials (ASDSO) produce cost estimates every few years to create awareness

on how much money is needed to rehabilitate dams in Virginia and in all the United States. DCR

estimates are sent to the Virginia Governor while ASDSO estimates are sent to Congress. Table

1.2 shows the ASDSO cost estimates from the past decade. The cost of dam rehabilitation and

repair is projected to increase with each passing year because the rate at which dams are being

repaired is currently not fast enough to keep up with the rate at which dams are aging and degrading

(ASDSO 2019). The federal government provides grants through the Water Infrastructure

Improvements for the Nation Act (WIIN) to assist dam owners with their projects. The 2019 WIIN

budget for dam safety grants was $25 million.

Table 1.2 ASDSO repair cost estimates for all dams in the U.S. regardless of Hazard Class

(ASDSO 2019)

In 2011, the DCR made an estimate of $592 million for all of Virginia’s state regulated

significant and high hazard dams. Despite this high estimate, they currently only budget about one

million dollars each year for dam rehabilitation and flood protection project grants. Table 1.3

shows how much of the DCR’s grant money was awarded to dam owners between 2017 and 2019.

3

Table 1.3 Virginia DCR grant program awards to local government and privately owned dams

There is a large funding gap between the amount of money needed to repair the nation’s

dams and the amount of money that is currently available through grant programs. Awareness on

this issue is raised each time the ASDSO or DCR release a new estimate. To maintain credibility,

it will become important to validate the estimates of these organizations and to evaluate whether

new cost estimate methodologies should be implemented. The ASDSO has not changed their

approach to cost estimating since 2002 despite all the new data that exists. The 2011 DCR estimate

of $592 million only considered 440 (16%) of Virginia’s 2,790 dams. For government leaders to

feel confident in the funding decisions they make for dam infrastructure, they will first need to feel

more confident on the cost estimates that they are given.

1.3 Purpose and Objectives

This research focused on the cost of dam rehabilitation in the Commonwealth of Virginia.

Data was collected for a sample of Virginia dams that have had rehabilitation projects of more

than $20,000 in the last 20 years. The data included dam characteristics, or factors, that may

potentially influence the cost of a rehabilitation project. The purpose of the research was to

examine and compare several different factors of dam rehabilitation to determine how they can be

used to make future cost estimates. This new cost estimating approach is offered as a possible

alternative to the DCR and ASDSO cost estimating methods which have relied on older and less

detailed data than what was collected in this study. To accomplish the purpose of this research, the

project was broken down into the following objectives:

● Objective 1: Conduct a thorough literature review that includes content on the Virginia

Dam Safety Standards and relevant policies, content on the repair and rehabilitation options

for dams, and content on the cost estimating methods that have been used by various

entities.

4

● Objective 2: Collect data for a variety of dam types in Virginia by means of phone calls,

emails, and/or published archives

● Objective 3: Construct a dam database that can be analyzed using various statistical

techniques.

● Objective 4: Perform statistical analyses on the data to identify what trends or patterns

exist.

● Objective 5: Compare cost estimates from previous years with the actual costs that have

been executed on completed projects to determine the accuracy of previous cost estimates.

● Objective 6: Create a new estimate for the cost of rehabilitating deficient Virginia dams.

5

Chapter 2 Literature Review

2.1 History of Dams in the United States

Dams have been used around the world for thousands of years to control watersheds for

the interests of mankind. Reservoirs provide water supply, irrigation, hydropower, and recreation

to people each day. Dams can also protect communities from flood events and control the levels

of water in rivers to assist with boat navigation. Because of the many benefits that dams provide,

the construction of these hydraulic structures became very prevalent in the development of the

United States. Engineering achievements such as the Hoover Dam and the Grand Coulee Dam

have benefitted millions of lives in the Western U.S. and have instilled a strong sense of American

pride. This was emphasized during Franklin D. Roosevelt's 1935 speech at the Hoover Dam

inauguration where he stated, “This is an engineering victory of the first order -- another great

achievement of American resourcefulness, skill and determination” (Roosevelt 1935).

The construction of dams boomed in what later became known as the “golden age” of dams

between 1950 and 1980. During this period, an average of 3 to 6 dams were being built per day

and any river that was not being dammed was considered wasted potential (Grabowski et al. 2018).

The failure of a few large dams in the late 1970’s, however, soon halted the rapid construction. A

concern for public safety quickly escalated after the loss of hundreds of lives. The Kelly Barnes

Dam failure in Toccoa Falls, Georgia that killed 39 people during the autumn of 1977 was the last

dam failure to occur before President Jimmy Carter issued an executive order for the inspection of

dams and floodplains nationwide (ASDSO 2019b). The United States Army Corps of Engineers

(USACE) were responsible for leading these inspections and discovered that many (if not most)

deficiencies existed in non-federally owned dams. These are dams that are not operated or

maintained by the federal government organizations (such as USACE or FERC) but rather, they

are owned by smaller entities such as private landowners or local governments. This discovery,

along with the simultaneous dam safety research being done by the National Academy of

Engineering and FEMA at that time, brought about the motivation and momentum to create the

Association of State Dam Safety Officials which officially formed on June 20, 1984 (ASDSO

2019b).

6

ASDSO was created during a time in which most states did not have dam safety laws or

programs. This organization has worked closely with each state to change these norms since 1984

and now 49 states have fully operating dam safety programs (ASDSO 2019b). ASDSO encourages

states to collaborate in dam safety efforts by sharing experiences and lessons learned with other

state programs.

Despite improvements since the 1980’s, dam safety is still a major concern in this country.

The 2017 failure of the Oroville Dam in California is the most recent reminder of the destructive

power of a deficient structure (ASDSO 2019c). For a country that currently contains over 90,000

dams (USACE 2018), it is critical that dam safety is held to the highest standards to ensure public

safety and resource security.

Lastly, it is important to note that, when constructed, most dams are given a life expectancy

of 50-60 years. Given that the “golden age” of dam construction was between 1950-1980, aged

dams should be of great concern. FEMA estimates that the operational life span of approximately

76,990 (84%) of America’s 91,457 dams will end by 2020 (Grabowski et al. 2018).

2.2 Virginia Standards for Dam Safety Compliance

The Virginia Department of Conservation and Recreation (DCR) is the dam safety

regulator for approximately 2,100 (75%) of Virginia’s 2,790 dams (DSIS 2020). Dams that are not

regulated by the DCR may be regulated by other agencies such as the US Army Corps of Engineers

(USACE), the Federal Energy Regulatory Commission (FERC) or the Virginia Department of

Mines, Minerals and Energy. This literature review focuses only on the policies and regulations of

the DCR. The DCR’s dam safety program works closely with state agencies, local governments,

and private dam owners to provide the proper and safe design, construction, operation, and

maintenance of dams for the interest of public safety.

2.2.1 Hazard Classifications and Design Criteria

Dams can be categorized by their hazard classification. The hazard class of a dam is

representative of how much downstream development would be at risk if the dam were to fail.

Hazard classification does not describe the condition of a dam. An old deteriorating dam and a

new well-maintained dam can both be considered low hazard if there are no homes or businesses

7

downstream. Table 2.1 describes the three hazard classifications for dams as defined by the DCR.

These classifications are a standard used in all 50 states.

Table 2.1 Hazard Classification Descriptions (DCR 2020c).

The hazard classification of a dam determines how large of a flood event the structure must

be designed to withstand. As would be expected, high hazard dams are required to resist larger

floods than low hazard dams. Table 2.2 shows the flood event design criteria that corresponds to

each dam hazard classification according to the Code of Virginia.

The Virginia Administrative Code (VAC) in the Code of Virginia, defines the probable

maximum flood (PMF) as the flood that might be expected from the most severe combination of

critical meteorological and hydrologic conditions that are reasonably possible in the region

(4VAC50-20-40). Although considered an extremely rare event, newly constructed high hazard

dams must be designed to resist a PMF. The PMF for any given location is calculated based on

several relevant factors such as land cover, soil conditions, and the corresponding probable

maximum precipitation (PMP). The PMP is defined as the greatest depth of precipitation for a

given duration that is physically possible over a given size storm area at a geographic location for

a certain time of the year (AWA 2018). The PMP value for any given location can be found using

the DCR’s PMP Evaluation Tool and Database (DCR 2020d). Low hazard dams do not need to

consider the PMF design criteria. Instead, they consider the 100 year flood event. This is the flood

event for which there is a 1% chance of being exceeded each year.

8

Table 2.2 Impounding Structure Regulations for Virginia as of 2008 (4VAC50-20-40)

2.2.2 Hazard Creep and Reclassification of Dams

Prior to 2008, a different classification system and design criteria existed in Virginia. There

were four categories of classification as opposed to the three that are used today. Furthermore, the

size of a dam was taken into consideration, which allowed for small dams to have less stringent

regulations to follow. Table 2.3 shows the details of the Virginia impounding structures regulations

prior to the year 2008.

Table 2.3 Impounding Structure Regulations for Virginia Prior to 2008 (4VAC50-20-50).

A comparison of Tables 2.2 and 2.3 shows that dams between 25 and 40 feet tall were the

most affected by these regulation changes. Many small dams that had been meeting regulations

prior to 2008 would have to upgrade their spillway capacities to meet the new standards.

In addition to the new design criteria, the 2008 legislation changes also evaluated the

hazard creep of many dams and reclassified them to riskier classes. Hazard creep occurs when

there is development downstream of a lake or reservoir that did not exist during the original

construction of the dam (Pisaniello and Tingey-Holyoak 2017). Hazard creep is common for a lot

of older dams that were constructed at a time when the surrounding areas were still very rural, but

9

that have experienced significant land development in recent decades. Unfortunately, a dam owner

has little to no control of what people decide to do downstream of a dam. Many people may have

built homes or businesses downstream of a reservoir without realizing the safety implications that

those locations could pose. In 2008, many dams that were found to have had downstream

development were reclassified to need a higher spillway capacity. It was common for a dam that

had once been considered Class II (possible loss of life) to be reclassified as a high hazard dam

(probable loss of life). In most of these situations, the spillway would have to be redesigned to

meet a full PMF instead of a partial PMF even if the spillway appeared to be in good condition

with no degradation (Pisaniello and Tingey-Holyoak 2017).

The 2008 dam safety regulation changes caught many dam owners off guard. Spillway

rehabilitation projects can be complicated and expensive and not all dam owners were prepared

for this regulatory change. In 2020, there are still numerous dam owners that have not upgraded

their dams to meet the new criteria.

2.2.3 Changes to PMP Values in 2016

The PMP values used today are not the same values that have always been used. In 2014,

Governor Terry McAuliffe authorized a new Virginia Probable Maximum Precipitation Study to

update the values based on the more modern computational and satellite technologies that were

now readily available. An interdisciplinary group of weather and water scientists collaborated in

this endeavor which was overseen by the (DCR 2020e). The study was completed in December of

2015 and the new PMP values went into effect on March 23, 2016 (DCR 2020d).

For some regions of Virginia, the new PMP value was higher than what it had previously

been. In other regions, values stayed the same or were lower. The locations that had an increase in

PMP also had increases in the PMF which is computed directly from the PMP value. With higher

PMF values, design criteria for dam spillway capacities became stricter. Conversely, the locations

that saw a decrease in PMP values saw decreases in the PMF value and could therefore relax their

dam spillway capacities. Many dam owners that were aware of this study during 2014 and 2015

stalled or halted dam rehabilitation projects to see how design criteria would change for their

location given the new PMP values.

10

2.3 Enforcing Dam Safety

For dams that are regulated by the state, dam owners are expected to have an Operation

and Maintenance Certificate (O&M Certificate). To obtain this, dams must meet the design

guidelines set forth in Table 2.2 in addition to having an Emergency Action Plan, paying

appropriate fees, and having annual engineer inspections (DCR 2014). These certificates are issued

for a six year period but can be taken away before the full 6 years if an issue is discovered during

an inspection.

If a dam does not meet all necessary requirements for an O&M Certificate, but does not

pose imminent danger, then the dam owner can apply for a Conditional Certificate (DCR 2014).

Conditional Certificates are issued for two years and include a list of the deficiencies that need to

be corrected. If the dam owner is unable to address all deficiencies in this two year period, they

can reapply for another Conditional Certificate. There is no limit on how many times a dam owner

can reapply for Conditional Certificates and it is possible to operate without all the O&M

requirements for several years with no penalties. This flexibility allows dam owners to have the

necessary time to accumulate project funds and prepare project plans.

2.4 Rehabilitation Options for Dams

Rehabilitation is defined as the “repair, replacement, reconstruction, or removal of a dam

that is carried out to meet applicable State dam safety and security standards” (WIIN 2016). The

goal of rehabilitation is always to keep the surrounding communities safe from catastrophic

flooding. There are many rehabilitation options for the various types of dams that exist, but this

section will briefly cover some of the most common practices. Earth embankment dams make up

over 70% of all Virginia dams (NID 2018) and these are also the most frequently rehabilitated.

Figure 2.1 shows the components of a typical earthen dam that are usually considered for upgrade

when completing a dam rehabilitation project.

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Figure 2-1 Components of a Typical Earthen Dam (FEMA P-911 2016)

2.4.1 Spillway Design Flood Upgrade Projects

Modifications to the principal and auxiliary spillways are very common in dam

rehabilitation projects. This is, in part, due to the Virginia regulation changes mentioned

previously. This can also be due to weathering or damage from large storm events such as tropical

storms or hurricanes. A dam’s auxiliary spillway is very rarely activated, but when it is, the

prevention of a catastrophic flood may depend on its integrity.

Many auxiliary spillways were originally constructed using the same earthen materials as

the dam. Recent rehabilitations, however, have been upgrading these to be stronger by such

methods as implementing roller compacted concrete (RCC) or articulating concrete blocks

(ACB’s) (Hepler et al 2018). Spillways can also be widened or lengthened to increase the amount

of water that can safely travel through. Spillway rehabilitations can be expensive and complex

depending on how much the capacity needs to be increased to ensure safety.

2.4.2 Other Upgrades

In addition to spillway modifications, dam walls can either be raised or widened to allow

for more storage. Sometimes individual components such as the outlet gate or toe drain need to be

repaired or replaced. The principal spillway riser often contains a trash rack to collect litter and

debris and this may need to be replaced after some time. Furthermore, dam owners should inspect

for rusting pipes and leaks that may be weakening a dam’s internal integrity. Concrete components

12

may need to be grouted if cracks start to appear. Dams that have accumulated too much sediment

may need to be dredged and dams that have let trees or bushes overgrow may need to be cleared.

The required project type is determined during engineering inspections and preliminary designs

and it is up to the owner to find the funds and the resources to ensure all components are up to

standards (DCR 2014).

2.4.3 The Environmentalist Movement Towards Dam Removal

Perhaps the riskiest and most complicated dam rehabilitation option is dam removal. This

option, however, is strongly advocated for amongst several environmental conservation

organizations (American Rivers 2020). It is a favored option for dams that no longer serve their

original purposes and for dam owners who no longer want to take on the responsibilities of

operation and maintenance.

The early 2000’s saw the largest decline in dam construction and currently the rate of dam

removals has outpaced the construction of new dams (Grabowski et al. 2018). Dam removal is

about more than dam safety, however. Proponents of removal projects believe that dams “block

the arteries of mother nature” and that “river systems should be restored to natural conditions”,

especially if a dam no longer serves its original purpose (Knight 2014). Environmentalists have

been protesting dams for decades and in 2014, the documentary DamNation received a lot of

attention for shedding light on the many negative environmental impacts of dams.

Dams completely alter the ecosystem of a watershed. They can destroy habitats and block

fish migrations. They block sediment transport which in turn stops nutrients from being carried

downstream (Knight 2014). The lakes and reservoirs behind dams have also been known to emit

large quantities of carbon dioxide and methane due to the decomposition of vegetation at the

bottom of the water body. It is enough greenhouse gas emission to bring into question whether

hydropower can really be called “clean energy” (Giles 2006). It is for these reasons that the dam

removal option has gained traction in the world of dam rehabilitation. Current trends indicate that

at least 4,000 dams will be removed in the United States between 2020 and 2050 (Grabowski et

al. 2018).

Balancing societal needs with environmental impact has never been easy for decision

makers regardless of what field of science or engineering is being discussed. In the case of dams,

it may be hard to justify that the migration of salmon is more important than providing drinking

13

water to a community. The critical thinking and collaboration from many interdisciplinary scholars

and professionals will be needed to decide which dams are acceptable to remove and which ones

are not (Grabowski et al. 2017).

2.5 Funding Assistance and Grant Programs for Dam Rehabilitation

2.5.1 USDA Natural Resources Conservation Services Funding for Dams

In August of 1954, the Watershed Protection and Flood Prevention Act (PL-566)

authorized the USDA Natural Resources Conservation Services (NRCS) to work with the smaller

units of governments to implement watershed projects that would resolve many of the flood

problems that were occurring around the country. As a result, thousands of new dams were

constructed around the US, especially in rural areas where agricultural lands and small towns

needed to be protected. In Virginia, approximately 150 dams were built with assistance from the

NRCS after the passing of PL-566 (NRCS 2020). These dams are owned by local governments

such as towns, municipalities, counties, or Soil and Water Conservation Districts (SWCD), and

are eligible for rehabilitation funding assistance through the NRCS due to The Small Watershed

Rehabilitation Amendments of 2000 (H.R.728). Dams are only eligible for rehabilitation

assistance if they are at, near, or past their original life expectancy. Eligible rehabilitation projects

can receive up to 65% of the cost through federal funding from PL-566 if that amount does not

exceed 100% of the total construction cost. In Virginia, 13 dam rehabilitations have been

completed with the assistance of NRCS. All these projects were multi-year and multi-million

dollar projects intended to increase each dam’s life expectancy for another 50 to 60 years (NRCS

2020).

2.5.2 WIIN Federal Funding for Dams

In 2016, Congress passed the Water Infrastructure Improvements for the Nation (WIIN)

Act to assist with all types of water projects from watersheds and waterways to drinking water and

wastewater (WIIN 2016). Section 5006 of the act discusses the grant program that was created for

the rehabilitation of high hazard dams. To be eligible for a WIIN grant, a dam must be classified

as a high hazard structure that fails to meet minimum dam standards or poses some type of risk to

14

the surrounding communities. The dam must also have a state approved Emergency Action Plan

to be considered. NRCS dams and federally owned dams are not eligible for these grants.

The dam rehabilitation program of WIIN was authorized for $10 million for fiscal years

2017-2018, $25 million for 2019, $40 million for 2020, and $60 million for 2021-2026. This is a

total of $445 million over ten years. Each year, the first ⅓ of available funding is distributed

equally among the states that apply for WIIN grants. The remaining ⅔ are then distributed based

on need (states with more high hazard dams will receive more funds). For each individual project,

WIIN will fund no more than 65% of the cost leaving the non-federal sponsors of the dam (local

communities and nonprofit organizations) to pay the remaining 35% of costs.

2.5.3 DCR Funding for Dams

The Virginia DCR has grants and loans to assist public and private dams that are regulated

by the state. The grants are awarded through a competitive application process and received as

reimbursements after the completion of the project. Federally owned dams are not eligible because

they are not regulated by the state. NRCS dams are eligible for this program, however. The dam

owner must be able to match at least 50% of the amount awarded by a DCR grant. The DCR can

award about $1,000,000 each year through grants, but this is split between dam safety projects and

other flood mitigation projects that may not necessarily involve a dam. Table 2.4 shows the

amounts that have been awarded for fiscal years 2017-2019. For the current 2020 cycle, the DCR

plans to use at least $600,000 of their million dollar budget for dam safety projects and a maximum

of $400,000 for other flood prevention and protection projects (DCR and VRA 2019).

Table 2.4 DCR Dam Safety and Floodplain Management Grants for 2017-2019 (DCR 2020b).

2.5.4 Miscellaneous Grants

In addition to the big grant programs that are managed by the NRCS, the WIIN Act, and

the DCR, smaller grant programs exist to help dam owners with rehabilitation projects. These

15

programs may be run by either government or non-governmental organizations (ASDSO 2019a).

Some of the government organizations include the Environmental Protection Agency (EPA), the

United States Fish and Wildlife Services (USFWS), and the National Oceanic and Atmospheric

Administration (NOAA). Some of the non-governmental organizations include the Nature

Conservancy, Trout Unlimited, and American Rivers. These different organizations provide small

sources of funding for dam rehabilitation projects that align with the goals and mission of that

organization. For example, the NGO American Rivers will assist with dam removals as part of

their mission to protect and restore wild rivers (American Rivers 2020). The NGO Trout Unlimited

will also be involved with dam projects if the project is expected to improve the quality of cold-

water fisheries. Dam rehabilitation projects, especially removals, can involve many different

entities and interest groups which can often open many unique funding opportunities. Grants

continue to be competitive, however, regardless of the funding source. Therefore, it is important

to identify and prioritize the dams that are in most need of an upgrade.

2.6 The Cost and Risk of Not Upgrading a Dam

It is evident that the cost of upgrading a dam can be quite high and that paying for these

upgrades is not something dam owners are willing to do unless it is deemed completely necessary.

To make the decision, there needs to be an analysis of risk and an analysis of cost-benefit ratios,

neither of which is an exact science.

The 1980’s introduced the idea of risk analysis which would fundamentally change the

practice of dam safety engineering in the United States (France and Williams 2017). Prior to that,

dams were evaluated simply on visual inspections and deterministic criteria. Deterministic criteria

include such things as calculating that the spillway capacity could handle a 100 year storm or

calculating that the stresses in structures were less than the ultimate strengths of the materials of

the dam (France and Williams 2017). In other words, dams were only evaluated on their current

state. Risk analysis introduces a consideration for the future state of a dam. It evaluates how likely

a dam failure is to occur and estimates how much damage that failure could result in. Many

methods exist to evaluate and quantify the risk of a dam, but all methods come with large amounts

of uncertainty (France and Williams 2017). Getting a sense for how “risky” a dam is may be useful

to owners who need to decide whether to upgrade a dam structure.

16

In addition to understanding the risk of a dam, it is useful for a dam owner to know how

much the failure of a dam would cost if it were to occur. Large floods can destroy both lives and

property. Such an event can also cause a loss of income for commercial, agricultural, and industrial

areas that cannot sell products or services until the flooding has receded and the damage has been

fixed (Ellingwood et al. 1993). Furthermore, there may be a deterioration of scenic beauty, cultural

heritage, or environment that may take years to restore. All these items would likely come at a cost

much higher than the cost of having rehabilitated the dam in the first place (Ellingwood et al.

1993). Dam owners may find that the benefit of preventing all this damage may greatly outweigh

the cost of rehabilitation and repair.

2.7 Previous Cost Estimating Studies and Reports

Before any level of government can decide how much money to appropriate for the

rehabilitation of dam infrastructure, there needs to be a cost estimate from a credible source to

guide the decision making and policy writing process. Various cost estimates are made every few

years by different organizations using different data sources and methodologies. Estimates raise

awareness on the importance of dam infrastructure investment, but it is ultimately up to

government leaders as to what action will be taken.

2.7.1 Cost Estimates from ASDSO

In 2001, the Association of State Dam Safety Officials formed a task group with the duty

of creating a report that would provide a reasonable estimate on the cost of rehabilitating the

nation’s dams (ASDSO 2019). Between 2002 and 2003 they investigated project costs from

approximately 300 dams across 22 states and used this existing data to create estimates for future

projects. The task group created a methodology that categorized dams by size and by hazard class.

Based on the size, hazard class, and type of work needed on a dam, an estimate could be made for

a dam project. The ASDSO used the National Inventory of Dams (NID) to determine how many

dams corresponded with each type of estimate and summed all the project costs to create one large

estimate for the whole country that was published in 2003.

Since 2003, the NID has added several thousand more dams to its inventory thanks to better

data collection methods. ASDSO has taken this increasing number and economic inflation into

consideration as they update the cost estimate every few years. Although ASDSO estimates are

17

not always made during the same years as ASCE Report Cards, the ASCE report card will still use

the latest ASDSO estimate when determining dam infrastructure grades. The most recent ASDSO

estimate was made in 2019 and placed the total cost of upgrading all dams in the US at about $65

billion. This includes all 90,000 dams in the NID regardless of hazard class, ownership type, or

level of urgency. The estimate they made for addressing only high hazard dams was about $21

billion.

Typically, the ASDSO only makes estimates for the nation, but in 2012 they decided to

investigate each state more closely. They used their methodology to come up with an estimate for

each state and then sent those estimates to the states for review and feedback. States would

determine if the estimate needed to be modified or if it could be deemed reasonable. For the state

of Virginia, it was estimated that $1.12 billion would be needed to upgrade all Virginia dam

infrastructure (ASDSO 2019).

2.7.2 Cost Estimates from the DCR in 2011

In 2011, the DCR prepared a cost estimate report for the Virginia Governor at the time,

Bob McDonnell. The goal of the report was to identify the dams that were in highest need of repair

and estimate how much it would cost to bring those dams up to the standards set forth by the Dam

Safety Act changes of 2008 (DCR 2011). Unlike the ASDSO studies that try to create a bulk sum

of all possible dam rehabilitation projects, the DCR focused on just 117 high hazard and 323

significant hazard dams from Virginia. To approximate the cost of upgrading these 440 dams, the

DCR mailed surveys to dam owners asking for their individual cost estimates. Unfortunately, there

was a very low response rate of about 6%. From the responses they were able to get and from

information that was available in the NID, the DCR created an empirical formula to estimate the

cost of upgrading the dams they had identified. This empirical formula was based on a dam’s

hazard class and the additional spillway capacity needed. Estimates obtained from the formula

were then sent to regional dam safety engineers to check and adjust as they saw fit from their

experiences with dam inspections. Table 2.5 shows the total cost estimates reported to the governor

from this study.

18

Table 2.5 Total Cost Estimates from the 2011 DCR Report for Virginia Significant and High

Hazard Dams

2.7.3 Cost Estimates from the DCR in 2018

In 2016, the DCR began a new cost estimating study for the Commonwealth of Virginia,

this time focusing on a more specific subset of dams than that of the 2011 study. This new

investigation looked only at the high hazard dams owned by the various Virginia Soil and Water

Conservation Districts (DCR 2018). These dams are local government owned and can typically

qualify for assistance through the NRCS funding program described earlier in section 2.4.1.

In total, there are 66 high hazard dams owned by the Virginia Soil and Water Conservation

Districts. Dams that had adequate spillway capacities or that were already in the process of

rehabilitation were removed from the study leaving 43 dams for investigation. The study of these

43 dams took place between 2016 and 2018. Engineers were hired to perform hydraulic analyses

and preliminary designs for each dam. These studies were then used to come up with cost estimates

for each of the 43 dams.

It was estimated that a sum of approximately $189.2 million would be needed to upgrade

these 43 high hazard district-owned dams. A detailed report with the methodologies, results, and

recommendations of this study were sent to Governor Ralph Northam on November 1, 2018.

2.8 Summary

Dams have played an important role in shaping America’s landscapes throughout history.

Unfortunately, many dams no longer meet state dam safety regulations due to aging, hazard creep,

or both. In the present day, dam engineering efforts are rarely used to build new dams, but instead

are used to rehabilitate or remove older dams. Fixing the problem of unsafe dam infrastructure is

expensive and many dam owners struggle to pull together the necessary funds. Different

19

government agencies and non-governmental organizations have worked to provide grant programs

to assist dam owners with the expenses, but budgets are tight, and these awards are competitive.

Over the years, several government task committees have worked to come up with cost estimating

and risk analysis methods to assist policy makers in their decisions about funding allocations, but

some estimates have been made with very limited data availability. Credible estimates need to be

repeatedly made so that awareness can continue to be raised on the matter of dam infrastructure

investment. Safe dams are critical for the safety of communities and non-compliant dams must not

be ignored.

20

Chapter 3 Cost Trends and Estimates for Dam

Rehabilitation in the Commonwealth of Virginia

3.1 Introduction

Throughout history, dams have played a large role in the growth and development of

communities because of their ability to provide essential services such as flood control, water

supply, and hydropower. In the United States, the construction of dams peaked between 1950 and

1980 in what later became known as the “golden age” of dams. During these years, an average of

3 to 6 dams were built across the U.S. each day and any river that was not dammed was considered

wasted potential (Grabowski et al. 2018). When constructed, most of these dams were given a life

expectancy of approximately 50 to 60 years. As many of these dams are now reaching and

exceeding that life expectancy, the need for rehabilitation projects is increasing in demand. Figure

3-1 shows the mean and median ages for dams in Virginia grouped by ownership type.

Figure 3-1 Mean and median ages of dams in Virginia categorized by ownership type (NID

2018).

21

In addition to age, downstream development is of large concern to many older dams. A lot

of these dams were built at a time when the surrounding areas were still very rural and dam safety

regulations could be less stringent (Pisaniello and Tingey-Holyoak 2017). As the population and

number of properties downstream of a dam begin to grow, the structure may need to be redesigned

to be more robust, not because the dam has aged and weathered, but due to the added risk

(Ellingwood et al. 1993).

The Virginia Department of Conservation and Recreation (DCR) is responsible for

regulating most of Virginia’s dams. Dam owners can go through a certification process with the

DCR to ensure that all state regulations are being met. Figure 3-2 shows the number of certificates

that have been awarded as of February 2020. Dams that are granted a Regular Operation and

Maintenance (O&M) Certificate are in full compliance. Conditional certificates are given to dams

that do not meet all regulations and require some type of rehabilitation work. Small, low hazard

dams can sometimes qualify for general certificates which have less requirements since loss of life

is unlikely if the dam were to fail. Small dams in agricultural settings can often be exempt from

the certification process entirely. Currently, only 302 of Virginia’s 2,790 dams (11%) have an

O&M Certificate. 384 dams are operating under conditional certificates and require upgrade work

within the next couple of years. 1,934 dams have not gone through the certification process yet

and it is unknown whether they need major upgrades (DSIS 2020).

Figure 3-2 Certificates granted by the DCR as of February 2020 (DSIS 2020).

22

There are many rehabilitation options for dam owners who are trying to switch from a

conditional certificate to an O&M certificate. Rehabilitation is defined as the “repair, replacement,

reconstruction, or removal of a dam that is carried out to meet applicable State dam safety and

security standards” (WIIN 2016). Sometimes rehabilitation can be as simple as replacing a trash

rack or repairing the outlet structure. Other times, rehabilitation projects can be very complicated,

especially if the hydraulics of the system are greatly altered as is the case with spillway

modifications or dam removals. Rehabilitation is important for ensuring that a dam can continue

to operate safely and effectively, but it can often come at high financial costs for dam owners. It

may take several years to gather all the necessary funds for a project. During that waiting period,

stakeholders must hope that no abnormally large storm event breaches the dam.

Dam rehabilitation funding in Virginia is limited and competitive. The DCR currently

distributes approximately $1 million each year to dam rehabilitation and floodplain management

projects across the Commonwealth. This is inadequate compared to the estimates that have been

made by the DCR and the Association of State Dam Safety Officials (ASDSO) shown in Table

3.1. ASDSO and the DCR have released several cost estimates since 2011 with the goal of

increasing awareness about the need for investment in America’s dams. ASDSO reports are sent

to Congress while DCR reports are sent to the Governor of Virginia. Published cost estimating

reports will vary greatly depending on what types of dams were considered in that study. Knowing

how many dams were considered in a cost estimate is important for understanding the meaning

and significance behind the dollar amount listed.

Table 3.1 Previous Cost Estimates for Virginia Dam Rehabilitations (DCR 2011, ASDSO 2019,

DCR 2018)

23

The estimates made in 2011 and 2012 have become outdated now that almost a decade has

passed, and the conditions of dams have changed. A new estimate is needed that considers which

projects have already been completed and which new projects are needed. When making estimates,

certain dam characteristics are often considered to influence the project costs. For example, the

ASDSO estimate categorized dams by their height because of the assumption that taller structures

would cost more to rehabilitate (ASDSO 2019). Other cost estimating methodologies may consider

different factors such as a dam’s age, drainage area, hazard class, ownership type, or rehabilitation

needs. Which factors have the most influence on the cost of dam rehabilitations for the

Commonwealth of Virginia? What factors have been considered in past cost estimate reports and

were those estimates successful? What factors should be considered to make future cost estimates

more accurate? Accuracy of cost estimating is important for obtaining credibility and future

government support with dam projects. This paper examines and compares six different factors of

dam rehabilitation to determine how they can be used to make future cost estimates.

3.2 Data Collection

The DCR has created a Dam Safety Inventory System (DSIS) where information for all of

Virginia’s dams is kept. The DSIS contains information on each dam’s size, location, purpose,

owner, certificates, etc. The DSIS is updated each time a dam owner submits some type of

paperwork for their dam; thus, the database is receiving new information on a near weekly basis.

This study uses a version of the DSIS that was downloaded in February 2020. Although the DSIS

is not accessible to the public, the DCR provides limited access to researchers. Data fields from

the DSIS that were relevant for this research were age, height, drainage area, ownership type and

hazard classification. The DSIS does not contain any information on dam rehabilitation costs.

To determine which of Virginia’s 2,790 dams have experienced rehabilitation work, a list

of alteration permits from the last 20 years was requested and obtained from the DCR. 357 dams

in Virginia have been approved for an alteration project since the year 2000. The list provided by

the DCR contained the names of these 357 dams but did not provide details of what the projects

entailed. Thus, individual dam owners were contacted to inquire about rehabilitation projects. Of

the 357 dams from the alteration permit list, 223 of these dam owners were contacted for

information. The initial contact was a brief email explaining the research and asking if the dam

owner was able to participate. If the dam owner responded positively, a survey about the

24

rehabilitation project and cost was sent. Some dam owners responded to the initial email saying

that there was no data to share (documents were lost when there was a change of dam owner).

Other dam owners responded that the alteration permit was used for something irrelevant to the

structure’s integrity such as the installation of cameras or monitoring stations. These projects were

disregarded for this study. For the most part, however, dam owners did not respond to the initial

inquiry. The responses from the 223 contacted dams are illustrated in Figure 3-3.

Figure 3-3 Responses from the contacted dams.

3.3 Analysis Methods

3.3.1 Consideration for Inflation

Data collected in this study was for projects completed between the years 2005 and 2020.

It was necessary to consider economic inflation to ensure that project costs were being analyzed

appropriately. In the construction industry, it is common to use index values to convert the cost

between two years using Equation 3.1,

𝑖𝑛𝑑𝑒𝑥 (𝑦𝑒𝑎𝑟 𝐴)

𝑖𝑛𝑑𝑒𝑥 (𝑦𝑒𝑎𝑟 𝐵)∗ 𝑐𝑜𝑠𝑡 (𝑦𝑒𝑎𝑟 𝐵) = 𝑐𝑜𝑠𝑡 (𝑦𝑒𝑎𝑟 𝐴) Equation 3.1

Index values can be obtained from several different sources. Three common index sources that

were considered for this study were RS Means, Engineering News Record (ENR), and the Bureau

of Reclamation’s Construction Cost Trends (CCT). Index sources are created using cost data from

various projects and cities around the US. No index value source has been made using Virginia

dam projects alone, but these three sources have been used by dam engineers, sometimes in

60, 27%

37, 17%126, 56%

Dam Owner Responses

Data Received No Data Available No response

25

combination (NRCS 2020). For this study, these three types of indexes were normalized to January

of 2020 and then averaged. All project cost data used in this study were normalized to 2020 costs

before analysis.

Figure 3-4 shows a graph of these normalized values to demonstrate how much inflation

has increased each year according to each source. When considering the average normalized values

from Figure 3-4, Equation 3.1 can be simplified to

𝑐𝑜𝑠𝑡 (𝑦𝑒𝑎𝑟 𝑜𝑓 𝑟𝑒ℎ𝑎𝑏)

𝑎𝑣𝑔.𝑖𝑛𝑑𝑒𝑥(𝑦𝑒𝑎𝑟 𝑜𝑓 𝑟𝑒ℎ𝑎𝑏)= 𝑐𝑜𝑠𝑡 (2020) Equation 3.2

Figure 3-4 Normalized historical cost index values.

3.3.2 Continuous Factors vs. Cost

Data from 60 Virginia dam rehabilitation projects were obtained for this study. Continuous

data fields in the database included dam age, height, and drainage area. Each of these factors was

tested against total project cost to determine whether a correlation existed. A strong correlation

may indicate that the factor is influential in a project’s cost. Two common statistical methods are

used for determining the strength of a correlation. One method is to calculate a Pearson correlation

coefficient, or R-squared value. This method is only valid when data has a normal, bell-shaped

distribution. When the data is non-normal, the Spearman correlation coefficient of rho is the

0.5

0.6

0.7

0.8

0.9

1

1.1

2004 2006 2008 2010 2012 2014 2016 2018 2020 2022

Norm

aliz

ed I

ndex

Val

ues

Year

Comparisons Between Different Types of Cost Indexes

RSMeans

CCT

ENR

AVG

26

preferred method (Gibbons and Chakraborti 2011). Figure 3-5 shows the distribution for the

project cost data and since the data appears non-normal, the Spearman rho method was chosen.

Figure 3-5 Distribution of rehabilitation project costs (n = 60).

Correlations in data can be visualized using scatter plots as shown in Figure 3-6.

Spearman’s rho describes the strength of that correlation with a single value. Rho values can range

from -1 to 1 where a value of zero would indicate that no correlation exists while a value of 1 or -

1 would indicate that there is a perfect positive or negative correlation. A perfect correlation would

mean that every data point lands on the trend line. Points that are far from the trend line may be

considered outliers. Outliers will be addressed in section 3.4.3 of this paper.

Figure 3-6 Continuous Factors vs. Total Rehabilitation Project Cost (n = 60).

Each of the rho values shown in Figure 3-6 can be validated using a hypothesis test. The

null hypothesis for the Spearman’s Rho Test is that no correlation exists (Ho: rho = 0; Ha: rho ≠ 0).

The null hypothesis is rejected when the p-value of the hypothesis test is found to be less than 0.05.

27

If the null hypothesis is rejected for p-values of 0.05 and below, there is at least 95% confidence

that some correlation exists. When the null hypothesis is not rejected, there is not enough evidence

to confidently state that a correlation exists. The p-values for the three correlations tested are shown

in Table 3.2. It was determined that at the 95% confidence level, all rho-values are valid. It is worth

noting, however, that the age vs. cost rho value is no longer valid when the confidence level is

raised to 96% as this would require a p-value less than 0.04. It is also worth noting that the scatter

plot in Figure 3-6 for Age vs. Cost shows that most dams were rehabilitated at approximately the

age of 50 years old. It is possible that age is a better indicator of when a project will occur, rather

than how much it will cost.

Table 3.2 Results from the Spearman’s Rho Hypothesis Test for Continuous Factors vs. Cost.

3.3.3 Categorical Factors vs. Cost

Categorical factors were also considered in this study. These included hazard

classifications, ownership type, and rehabilitation type. Dams can be classified as low, significant,

or high hazard depending on the quantity of people and property downstream that would be

affected by a dam breach. Dams can be owned by private citizens or organizations (such as

homeowner associations), local governments (such as towns or counties), state departments (such

as the VA Department of Game and Inland Fisheries), public utilities, or the federal government.

Data was obtained for private, local government, and state owned dams. Lastly, there are several

types of rehabilitation that a dam can undergo. These include but are not limited to raising or

widening the dam, modifying the spillways, replacing rusted pipes, or reinforcing the earthen

stability. Removing the dam is also a form of rehabilitation. This study separated dam

rehabilitation types into two categories. The first category was that of a single component project.

For example, only the spillway was modified and nothing else was done to the dam. The second

category of rehabilitation type was that of a multi-component project. An example of this is if a

dam was raised in addition to having its spillway modified. It is important to note, however, that

28

the type of rehabilitation needed may not be known until a full assessment and preliminary design

is performed on the dam. Such detail of information is typically not available when making large

general estimates, so it will be important to rely more on other factors when making cost estimates.

When dams are grouped by hazard class, ownership type, and rehabilitation type, they can

be visualized through box and whisker plots. Figure 3-7 illustrates the data grouped by categories

and in its entirety using box and whisker plots.

Figure 3-7 Box and whisker plots for the collected data holistically and for the collected data

separated into categories.

3.3.4 Continuous Factors vs. Cost Separated by Category

Previous sections identified the overarching trends of the data. In this section, correlations

are re-evaluated when dams are separated by categories. In total, there were 27 combinations of

analyses that could be performed listed in Table 3.3. As dams are divided into categorical

groupings, the original sample size of 60 becomes significantly reduced for each scenario.

Spearman’s Rho test was not performed on sample sizes smaller than 10 as this was considered

insufficient data to provide confident results.

29

Table 3.3 Correlation Analysis for Numerical Factors vs. Cost for Dams Separated by Category.

Notes: Items highlighted in light gray correspond to situations where Spearman’s Rho Test rejected the null hypothesis

proving that rho was valid. Items highlighted in dark gray indicate that the removal of outliers caused a failure to reject

the null hypothesis making the corresponding rho value invalid.

The 8 combinations of analyses that were found to have a valid rho correlation were then tested

for outliers as a further form of validation. In linear regression, outliers are identified when the

quotient of a data point’s residual and standard error is greater than the absolute value of 2 (Pardoe

2012). A residual is defined as

ei = Yi - yi Equation 3.3

where Yi is the expected value and yi is the value of the actual data point. Yi is obtained from the

linear regression model (trendline) in the form of

Yi = bo + b1*Xi Equation 3.4

30

where bo and b1 are the y-intercept and slope, respectively. The standard error is defined as

S = √∑(𝑌𝑖−𝑦𝑖)^2

(𝑛−2) Equation 3.5

When ei/S is greater than the absolute value of 2 for a given data point, that data point is considered

an outlier. If the outlier is removed from the data set, the outlier test should be performed again to

identify whether new outliers appear.

Once all outliers were removed from the combinations of interest, the Spearman’s Rho test

was rerun to determine if the same correlations still existed. The new rho and p-values are also

shown in Table 3.3. For two of the combinations, the new rho values were not valid because the

p-value was found to be greater than the acceptable 0.05 (highlighted in dark gray).

Outliers may be caused by time delaying situations such as severe weather, unexpected soil

conditions, or internal conflicts between stakeholders. Outliers need to be handled with caution,

especially if their cause is unknown, because they can greatly alter a regression model. Although

the removal of outliers can sometimes make models appear more accurate, the removal of outliers

could potentially be the removal of some important underlying information in the data. There are

two solutions for understanding outliers in this study. The first would be to reach out to dam owners

that provided data and inquire more information about the project conditions. The second would

be to collect more data from around the Commonwealth. For now, this study simply compares

results between data with outliers and data without outliers.

3.3.5 Theil Sen Regression Analysis

Theil Sen Regression is the non-parametric approach to linear regression where one

dependent and one independent variable are considered (Mangiafico 2016). This model takes the

form of

Yi = bo + b1*Xi Equation 3.4

For this study, Yi is the cost estimate, Xi corresponds to the value of the numerical factor being

considered, b0 is the y-intercept, and b1 is the slope of the model. Table 3.4 shows the regression

model for all combinations where the rho correlation value was found to be valid.

31

Table 3.4 Theil Sen regression models for all combinations with a valid rho correlation.

Multiple regression models could be used to estimate the cost of a single dam rehabilitation

project. For example, a high hazard and local government owned dam could use models 2, 3, 5

and 7 to obtain four different cost estimates. A weighted average could then be taken for those four

different estimates where the weight is determined by the strength of the data correlation, rho.

Another approach to cost estimating is to use the 95% confidence interval that surrounds

each regression model as shown in gray in Figure 3-8. Instead of using each model to obtain a

single estimate, each model would be used to obtain a range of estimates for which there is 95%

confidence. Consider the example of a 65 foot tall high hazard and local government owned dam

with a drainage area of 8 mi2. Figure 3-8 shows what each model would estimate for a dam of that

size. Note that circles indicate outliers and the vertical line indicates 65 ft height and 8 mi2. The

results are then tabulated in Table 3.5.

32

Figure 3-8 Models 2 (A/B), 3(C/D), 5(E/F), and 7(G/H) with and without outliers.

(A/B) represents Cost vs. Height for High Hazard Dams, (C/D) represents Cost vs. Height for Local Govt.

Dams, (E/F) represents Cost vs. Drainage Area for High Hazard Dams, (G/H) represents Cost vs. Drainage

Area for Local Govt. Dams

33

Table 3.5 Tabulated cost estimate results for one high hazard and local government owned dam

that is 65 feet tall and has a drainage area of 8 mi2.

3.4 Predictions of Future Costs

The Theil Sen regression models can provide an estimated range of cost for a dam

rehabilitation project based on some influential factors such as height, drainage area, hazard class,

and ownership type. For a more precise cost estimate, however, an engineer would need to evaluate

the specific needs of that dam, then estimate the cost in materials and labor hours. The Theil Sen

regression model approach is better suited for estimating the cost of rehabilitating a large number

of dams instead of one dam in particular. The benefit of having a general cost estimating approach

is that a total estimate can be made for hundreds of dams without the need to create preliminary

designs for each one. The estimate provided by the Theil Sen models may be sufficient to guide

government leaders in budgetary decisions.

The Commonwealth of Virginia has over 2,700 dams. A cost estimate for the 384 dams

with conditional certificates is needed to determine how much money the different levels of

government should be allocating. The developed models provide an estimate for the dams that are

high hazard and local government owned. More data needs to be collected before models for low

hazard, significant hazard, privately owned, and state owned dams can be made with confidence.

There are 98 high hazard and local government owned dams in Virginia that have a conditional

certificate. The estimate to rehabilitate these dams when considering the models that have outliers

is approximately $315 million. When models with no outliers are used, the estimate becomes $300

million.

34

3.5 Evaluating Estimates made by the VA DCR

In 2011 and 2018, the DCR was tasked with making estimates for the cost of rehabilitating

Virginia’s dams. The 2011 study made an estimate that focused only on state regulated dams that

were of significant or high hazard. The DCR used their own empirical formula based on spillway

capacity and made an estimate for 440 dams. This study determined the actual project cost for 17

of those dams and compared them to the 2011 DCR estimates. The comparison is shown in Table

3.6 and all dollar amounts were converted to the January 2020 value.

Table 3.6 Comparison of DCR’s 2011 estimates against actual project costs and against Theil

Sen estimates. The data is ranked by the DCR’s percent error.

For these 17 dams, a trend became apparent when the percent error was compared between

ownership types. The DCR significantly overestimated the costs of privately owned dams while

greatly underestimating the costs of local government and state owned dams. In general, privately

owned dam projects tend to spend less money than the local government and state owned projects.

More data needs to be collected as projects continue to be completed to determine if this is a

continuing trend.

In 2018, the DCR made a new estimate, but only for the dams owned by the Soil and Water

Conservation Districts (SWCD) which are considered locally owned and are all high hazard. The

Theil Sen models were used to estimate project costs for the same dams for comparison purposes.

35

The results are shown in Table 3.7, but the actual costs are still unknown, so accuracy of the two

estimates cannot be evaluated.

Table 3.7 Cost estimates of rehabilitating Virginia SWCD dams that need repair (DCR 2018)

3.6 Discussion and Conclusions

The biggest challenge in cost estimating studies is the availability of cost data from past

projects. This study was only able to use data from 27% of the 223 dams contacted. The 2011 DCR

study surveyed 1,267 dam owners and only received a 6% response rate. The DCR has made large

strides in data collection since 2011, however, with the implementation and growth of the DSIS

database. The DSIS contains a significant amount of information such as size, location, and

condition, but there is still no information about rehabilitation costs. Adding this type of

information to the database could allow for more successful future research in cost analysis studies,

which could lead to better funding solutions to help dam owners pay the costs of their projects.

Although the sample size used in this study was small compared to the number of dams

that have actually been rehabilitated in Virginia, the sample size was large enough to show some

strong trends that would likely continue as more data is collected. Dam height and drainage area

proved to be the strongest factors in determining the cost of a project, although the strength of the

factor varies depending on what category of dam is being evaluated. Age appeared to be a weak

factor in determining the cost of a project, regardless of dam category. Age is a more appropriate

factor for determining when a rehabilitation project will need to be done as most dam life

expectancies are approximately 50 to 60 years.

Collected data indicated that local government owned dam rehabilitation projects tend to

cost more than privately owned dam projects. This could be in part because the local government

owned projects tend to be larger and of high hazard classification. This could also be in part

because private dam owners often have tighter budgets and less flexibility in how they can spend

their funds. Local government dams may rehabilitate many components of the dam in a single

project while private dam owners tend to fix one component at a time.

36

Lastly, this study used Theil Sen regression models to come up with two comprehensive

estimates for dam rehabilitation in the Commonwealth of Virginia. The first estimate was

approximately $300 million for the repair of all local government owned high hazard dams with

conditional certificates. The second estimate was approximately $122 million for the repair of all

the SWCD dams that have not been majorly modified since the date of their construction in the

early 1950’s. The accuracy of these estimates may be determined in the coming years as dams

continue to be rehabilitated in Virginia.

37

Chapter 4 Conclusion

4.1 Implications

There are over 2,790 dams in the Commonwealth of Virginia and the conditions of these

dams change with each passing day. Currently, most dams are approaching or exceeding their

intended life expectancy, which has resulted in a high demand for dam rehabilitation. Although

the DCR tracks a lot of information about each dam such as size and location, they do not track

cost information about the rehabilitation projects that are completed. Tracking information about

the costs of rehabilitation work could not only help future cost estimators, but also hold certain

dam owners and agencies more accountable for the way grant money is spent on projects.

Although no cost estimate can be made with absolute confidence, there is certainty that the

cost of rehabilitating all deficient dams is much higher than what dam owners can currently afford.

There needs to be a continual effort in producing cost-effective solutions to deficient dams while

maintaining the highest standards of safety. Currently, the dam engineering community in the

United States is more focused on the repair and removal of existing dams than they are on the

construction of new dams and it can be expected that this trend remains true for many decades to

come.

Awareness of dam rehabilitation is important for both the general public and government

leaders. Cost estimates are used to inform people about the need for dam infrastructure investment

so it is important that these estimates can be made with as much accuracy and confidence as

possible. Cost estimates need to be continually assessed against completed project costs to

determine if estimating methodologies are accurate and reliable.

This research investigated a new cost estimating approach that used Theil Sen regression

models. Although this approach is not recommended for producing the cost estimate of one

individual dam, it may be helpful in providing an estimate for a large sample of dams. These

models estimated that approximately $300 million is needed in Virginia to address 98 deficient

high hazard, local government owned dams and that $122 million is needed to address Virginia’s

SWCD dams.

38

4.2 Future Work

The Theil Sen Regression models used in this research can be continually modified and

improved as more data is collected. Eight models were made in this study, but there is potential

for the creation of additional models if more data is collected for dams that are privately owned,

utility owned, low hazard, or significant hazard.

This study only considered the numerical factors of age, height, and drainage area. There

are several other factors that could be investigated in future studies such as dam height, dam width,

spillway capacities, or reservoir surface area. This study categorized dams by ownership type,

hazard classification, and rehabilitation type, but other categories could be used in future studies

such as dam type, dam purpose, or location.

A detailed study on the cost variance of dam rehabilitation based on location would be an

interesting study as dams could be separated between rural and urban areas or separated by

geographic region. A study that categorizes by location could also investigate the demographics

of the respective area and provide cost benefit ratios to possibly validate the higher costs of some

projects.

This study could also be done on other states. One possible study could investigate if the

Virginia models could be used to estimate dam rehabilitation cost in a neighboring state such as

North Carolina. Another study could be used to make models for various states that could be

compared. An understanding of the geographic distribution of dam rehabilitation spending across

the US could help determine where federal funds from the WIIN Act should be allocated first.

With so many dam characteristics to consider, there are a lot of options for future work in

this area of study. The first step, however, will be improving the accuracy and efficiency of data

collection. Strong data will make strong cost estimating models.

39

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Appendix A – Survey Questions

Dam owners who were willing to share information on their dam rehabilitation projects were sent

a survey with the following questions:

1. Name of contact filling out the survey

2. Dam name

3. County where the dam is located

4. Year that original dam construction was completed

5. Year that dam was rehabilitated

6. Brief description of the work that was done to the dam during rehabilitation

7. Total project cost

8. Of the total cost, how much was used for engineering services?

9. Of the total cost, how much was used for non-engineering services?

10. (Optional) Any additional comments?

Engineering costs and non-engineering costs for projects were also analyzed during this study, but no

conclusions could be drawn from the results. Total project cost was determined as the best value to analyze

and create estimation models for.

43

Appendix B – Sample of Dam Database

44

Appendix C –Spearman’s Rho Equations and R Code

Spearman’s Rho (ρ) Statistic (Gibbons and Chakraborti 2011):

ρ = 1 −6 ∑ 𝐷𝑖

2𝑛𝑖=1

𝑛(𝑛2−1)

Where n represents the total number of pairs,

Di = (Ri – Ravg) – (Si – Savg),

Ri = rank (Xi) and Si = rank (Yi)

In this study, Xi values corresponded to numerical factors such as a dam’s height or drainage

area. Yi values corresponded to total cost.

Spearman’s rho can be calculated in R Studios with the cor.test function. Rho was only

considered valid when the p-value from the hypothesis test was less than 0.05.

The following example tests the correlation between height and total cost for high hazard dams.

Input: cor.test(DataHigh$Height, DataHigh$Total_Cost, alternative = "two.sided", method = "spearman", conf.level = 0.95, continuity = FALSE)

Output:

Spearman's rank correlation rho data: DataHigh$Height and DataHigh$Total_Cost S = 1051.5, p-value = 0.0004238 alternative hypothesis: true rho is not equal to 0 sample estimates: rho 0.6405218

45

Appendix D – R Code Theil Sen Regression Models

Theil-Sen nonparametric regression, also known as Kendall-Theil regression, is the nonparametric

version of linear regression. In R Studios, the Theil Sen method computes the slope between all

pairs of points and then computes the median of all those slopes. That median slope value is the

slope of the regression model (Mangiafico 2016). To form the regression model for total cost vs.

height for high hazard dams, the following code is needed:

Input

library(mlbm)

model01<-mblm(Total_Cost~Height, data = DataHigh)

summary(model01)

Output

Coefficients: Estimate MAD V value Pr(>|V|) (Intercept) -1758319 2513051 52 0.00104 ** Height 66555 49787 350 5.96e-08 ***

Values under “Estimate” were used to make the regression model. So, in this example,

Total Cost = -1758319 + 66555*height

For a 65 foot tall dam, the fitted cost estimate and the upper and lower bound of the 95%

confidence range can be determined as follows:

Input:

library(car)

new.cost<-data.frame(Height = c(65))

predict(model01, new.cost, interval = "confidence")

Output:

fit lwr upr 1 2309246 1711743 2906749

Thus, the fitted estimate is $2,309,246 while the 95% confidence interval is between $1,711,743

and $2,906,749.

46

To visualize the regression model with the 95% confidence bands against the existing data, the

following code was used:

Input:

library(tidyverse)

library(ggplot2)

library(ggpubr)

sen <- function(..., weights = NULL) {

mblm::mblm(...)

}

p01<-ggplot(DataHigh, aes(x=Height, y=Total_Cost/1000000), xmin=0)+

geom_point(color='#2980B9', size = 2)+

geom_smooth(method = sen, color='#2C3E50')

p01 <- p01 + ggtitle("Cost vs. Height for High Hazard Dams w/o Outliers") +

xlab("Height(Ft)") + ylab("Total Cost in Millions of USD") + ylim(-3,12)

p01

Output: