Inspection, Maintenance
And Operation Of Dams
In Pennsylvania
COMMONWEALTH OF PENNSYLVANIA
DEPARTMENT OF ENVIRONMENTAL PROTECTION
Office Of Water Management
Bureau Of Waterways Engineering And Wetlands
Division Of Dam Safety
G1354-Mar13
PENNSYLVANIA DEPARTMENT OF ENVIRONMENTAL PROTECTION
DIVISION OF DAM SAFETY
THE INSPECTION, MAINTENANCE AND OPERATION
OF DAMS IN PENNSYLVANIA
2009 Edition
Reprinted 2013
Original Edition (1985) Prepared by
Karl H. Lewis, Ph.D
Daniel L. Bink, P.E.
Lois M. Muller
Department of Civil Engineering
University of Pittsburgh
PREFACE
This publication has been issued by the Pennsylvania Department of Environmental Protection
(PA-DEP), Division of Dam Safety for use by owners and operators of dams throughout the state. Its
purpose is to provide guidelines for inspection, maintenance and operation of these facilities. It is
intended to serve as an information resource and an educational tool for the dam owner/operator.
Familiarity with the information contained herein should help the dam owner/operator comply with his
responsibilities as established in the Dam Safety and Encroachments Act (32 P.S. §§693.1-693.27). This
manual will aid the dam owner/operator in developing adequate skills of observation and inspection and
increase his awareness of the elements of proper operation and maintenance.
Proper use of this manual should reduce the potential for dam failure and increase the overall safety of a
dam by improving operating reliability and maintenance. However, it is recognized that every dam is
unique and that this manual does not cover every feature of every possible condition which may develop.
Consequently, it should never be considered a substitute for the sound judgment of a qualified
professional engineer.
This publication is to be viewed as a supplement to, but not a substitute for, any of the provisions of the
Dam Safety and Encroachments Act (hereafter referred to as the "Act") or Pennsylvania's dam safety
regulations contained in the publication entitled Chapter 105, Rules and Regulations, Dam Safety and
Waterway Management (hereafter referred to as "Chapter 105").
It is recommended that the dam owner/operator place this manual in a three-ring binder notebook with
sufficient excess capacity to allow for the inclusion of additional future information. The extra space in the
notebook can be filled by such items as past inspection reports; operation and maintenance; design
and/or construction records; correspondence; and other information pertinent to the dam. This should
provide the minimum means whereby owners can keep accurate and up-to-date records of their dams.
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TABLE OF CONTENTS
Page
PREFACE .................................................................................................................................................... i
TABLE OF CONTENTS ............................................................................................................................... ii
ACKNOWLEDGEMENTS ........................................................................................................................... v
LIST OF TABLES ........................................................................................................................................ vi
LIST OF FIGURES ..................................................................................................................................... vii
SECTION 1.0 — BACKGROUND ............................................................................................................... 1
1.1
INTRODUCTION ............................................................................................................................ 2
1.2
COMMON DAM ELEMENTS ......................................................................................................... 2
1.3
TYPES OF FAILURES ................................................................................................................... 3
a.
Hydraulic ........................................................................................................................... 3
b.
Seepage ............................................................................................................................. 3
c.
Structural ........................................................................................................................... 4
1.4
MONITORING DEVICES ............................................................................................................... 4
SECTION 2.0 — DAM INSPECTION ......................................................................................................... 7
2.1
GENERAL ...................................................................................................................................... 8
a.
Introduction ....................................................................................................................... 8
b.
Pennsylvania Inspection Requirements ............................................................................ 8
c.
Inspection Preparation ...................................................................................................... 9
1.
Review Existing Data ........................................................................................... 9
2.
Gather Appropriate Inspection Equipment ............................................................ 9
a)
Required equipment ................................................................................ 9
b)
Recommended equipment .................................................................... 10
3.
Follow A Predetermined Inspection Sequence ................................................... 11
2.2
INSPECTION ITEMS ................................................................................................................... 11
a.
Embankment ................................................................................................................... 12
1.
Crest ................................................................................................................... 14
2.
Upstream Slope .................................................................................................. 16
3.
Downstream Slope ............................................................................................. 18
4.
Abutments and Foundations .............................................................................. 20
b.
Spillway ............................................................................................................................ 21
1.
Erodible Channels ............................................................................................... 21
2.
Non-erodible Channels ....................................................................................... 22
c.
Outlet Works ................................................................................................................... 24
d.
Miscellaneous ................................................................................................................. 27
1.
Reservoir ............................................................................................................. 27
2.
Monitoring Devices ............................................................................................. 27
3.
Metalwork ........................................................................................................... 28
4.
Concrete and Concrete Dams ........................................................................... 28
2.3
RECORDS .................................................................................................................................... 31
a.
Inspection Checklists ...................................................................................................... 31
b.
Photographs .................................................................................................................... 31
c.
Monitoring Data ................................................................................................................ 31
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TABLE OF CONTENTS
(Continued)
Page
SECTION 3.0 — DAM MAINTENANCE ...................................................................................................
3.1
INTRODUCTION...........................................................................................................................
3.2
AREAS OF REQUIRED MAINTENANCE ....................................................................................
a.
Embankment ...................................................................................................................
b.
Spillway ............................................................................................................................
c.
Outlet Conduit ..................................................................................................................
d.
Miscellaneous .................................................................................................................
3.3
MAINTENANCE ITEMS ...............................................................................................................
a.
Vegetation Control ...........................................................................................................
b.
Rodent Control .................................................................................................................
c.
Earthwork ........................................................................................................................
d.
Concrete ..........................................................................................................................
e.
Conduits (Outlet and Spillway) ........................................................................................
1.
Internal Maintenance ..........................................................................................
2.
Trash Racks .......................................................................................................
f.
Mechanical ......................................................................................................................
g.
Electrical ..........................................................................................................................
h.
Hydraulic .........................................................................................................................
i.
Miscellaneous .................................................................................................................
1.
Access Roads ....................................................................................................
2.
Monitoring Devices .............................................................................................
3.
Winterizing ..........................................................................................................
4.
Vandalism Prevention .........................................................................................
3.4
MAINTENANCE SCHEDULE ......................................................................................................
3.5
MAINTENANCE RECORDS ........................................................................................................
SECTION 4.0 — DAM OPERATION ........................................................................................................
4.1
GENERAL ....................................................................................................................................
a.
Introduction .....................................................................................................................
b.
Elements of an Operation Plan ........................................................................................
4.2
OPERATION PLAN ......................................................................................................................
a.
Section I — Background Data .........................................................................................
1.
Vital Dam Statistics ............................................................................................
a)
Embankment ..........................................................................................
b)
Spillway ..................................................................................................
c)
Outlet .....................................................................................................
2.
Descriptions of Appurtenances ...........................................................................
3.
Operating Instructions for Operable Mechanisms ..............................................
4.
Monitoring Instructions and Forms .....................................................................
5.
Maintenance Instructions ....................................................................................
6.
Information Bibliography .....................................................................................
7.
Telephone List ....................................................................................................
b.
Section II — Schedule of Routine Tasks .........................................................................
1.
Category 1 High Hazard Dams ...........................................................................
2.
Category 2 High Hazard Dams ...........................................................................
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32
33
33
33
33
34
34
34
34
34
36
36
36
36
36
36
37
37
38
38
38
39
39
39
39
40
41
41
41
41
41
41
41
41
42
42
42
42
42
42
42
42
43
43
TABLE OF CONTENTS
(Continued)
Page
c.
3.
All Non-High Hazard Category 3 and Category 4 Dams .................................... 43
Section III — Emergency Action Plan ............................................................................. 43
APPENDIX A
IMPORTANT TELEPHONE NUMBERS AND ADDRESSES .......................................... 47
APPENDIX B
INSPECTION CHECKLIST .............................................................................................. 51
APPENDIX C
REFERENCE LIST .......................................................................................................... 61
APPENDIX D
GLOSSARY OF TERMS .................................................................................................. 64
APPENDIX E
SUBJECT INDEX ............................................................................................................. 72
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ACKNOWLEDGEMENTS
(Original Edition, 1985)
Failures or near failures of several dams in the United States in recent years have resulted in an
increased emphasis on dam safety. Tragedies such as the collapse of the Buffalo Creek coal waste
embankment in West Virginia and the failure of the Canyon Lake Dam in South Dakota, both of which
occurred in 1972, led to the enactment of the National Dam Inspection Act of 1972 (P. L 92-367).
Failure of the Teton Dam in 1976 and Laurel Run Dam (Pennsylvania) and Toccoa Falls Dam (Georgia)
in 1977 resulted in the implementation of this statute by the federal government.
The U. S. Army Corps of Engineers in cooperation with the Department of Environmental Protection
(DEP) completed an intensive four-year inspection program including several hundred existing dams in
the state.
In 1978, the Pennsylvania Legislature enacted the Dam Safety and Encroachments Act (Act No. 325,
P.L. 1375). This statute was amended by Act No. 70 in 1979. In September, 1980, the Environmental
Quality Board adopted Chapter 105, Rules and Regulations, Dam Safety and Waterway Management.
The assistance and training provided by the Corps of Engineers during the four-year period of the
National Dam Inspection Program has been an invaluable asset in development the commonwealth's
dam safety program.
The experiences of other states, particularly Virginia, Ohio and Colorado have been utilized in the
development of this publication. The Bureau of Reclamation has also contributed many valuable ideas
through its Safety Evaluation of Existing Dams program.
It is noted that the cooperation of the owners of dams within the state is the keystone to the success of
the state's dam safety program. The response of most of the owners, both public and private, with whom
the Division of Dam Safety has come in contact as a result of the Inspection Program has been satisfying.
The ultimate purpose of such a program is the protection of the lives and property of the citizens of the
state. The ready acceptance of this goal by the majority of the wide range of individuals and groups
bearing the responsibility for the safety of dams is very much appreciated.
The information contained in this effort was collected and prepared by Daniel L. Bonk, P. E., and Lois M.
Muller, under the direction of Karl H. Lewis of the University of Pittsburgh. Administrative facilities and
assistance were provided by GAI Consultants, Inc. of Monroeville, Pennsylvania. Overall preparation and
editing was performed under the general direction of Joseph J. Ellam, Chief, Division of Dam Safety. The
Division of Dam Safety extends its gratitude and appreciation to all the above for their efforts and
assistance.
-v-
LIST OF TABLES
Table
Title/Description
Page
1.0
Common Monitoring Devices ............................................................................................. 5
2.0
Probable Causes of Embankment Conditions .................................................................. 12
2.1
Possible Harmful Effects of Embankment Conditions ...................................................... 13
2.2
Recommended Actions for Embankment Conditions ...................................................... 13
3.0
Rodents and Rodent Controls ......................................................................................... 35
3.1
Mechanical Maintenance Procedures .............................................................................. 37
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LIST OF FIGURES
Figure
Title/Description
Page
1
Common Dam Elements ................................................................................................. 2
2
3
4
Survey Monuments .......................................................................................................... 5
Inclinometer ...................................................................................................................... 5
Longitudinal and/or Transverse Cracks along Embankment Crest ............................... 14
5
6
Low Area in Dam Crest ................................................................................................. 15
Sinkhole or Animal Burrow Along Embankment Crest ................................................... 15
7
8
9
Erosion Behind Poorly Graded Riprap ........................................................................... 16
Whirlpool in Reservoir ................................................................................................... 17
Erosion at Embankment-Abutment Contact (Upstream Slope) ..................................... 17
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Wet Areas (no measurable flow) ....................................................................................
Erosion at Embankment-Abutment Contact (Downstream Slope) ................................
Bulging ...........................................................................................................................
Seepage Water Exiting as a Boil in the Foundation ......................................................
Trampoline Effect in Large Soggy Area ........................................................................
Leakage from Abutments Beyond the Dam ..................................................................
Slide, Slough or Scarp in Spillway Channel ..................................................................
Erosion in Spillway Channel ..........................................................................................
Excessive Vegetation or Debris in Erodible Spillway Channel .....................................
Spillway Wall Displacement or Misalignment ................................................................
Open or Displaced Spillway Wall Joints .........................................................................
Excessive Vegetation or Debris in Non-Erodible Spillway Channel ..............................
Outlet Pipe Damage .......................................................................................................
Debris Under Outlet Gate ...............................................................................................
Cracked Outlet Gate Leaf ..............................................................................................
Damaged Outlet Gate Seat or Guides ..........................................................................
Damage to Outlet Control Works ..................................................................................
Discharges from Outlet Eroding Toe of Dam .................................................................
Deterioration at Outlet Discharge Structure ..................................................................
18
19
19
20
20
20
21
21
22
22
22
23
24
24
24
24
25
26
26
29
30
31
32
Inoperable or Damaged Instrumentation .......................................................................
Longitudinal or Horizontal Concrete Cracking................................................................
Transverse or Vertical Concrete Cracking ....................................................................
Diagonal Concrete Cracking .........................................................................................
27
28
29
29
33
34
35
36
Random Concrete Cracking ...........................................................................................
Pattern Concrete Cracking .............................................................................................
Leakage through Concrete Joints or Cracks .................................................................
Monolith Misalignment ...................................................................................................
29
29
30
30
- vii -
SECTION 1.0
BACKGROUND
-1-
SECTION 1.0 — BACKGROUND
1.1
Introduction
Water stored behind a dam represents potential energy which can create a hazard to life and property
located downstream. At all times the risks associated with the storage of water must be minimized. Dams
must be properly designed, constructed, operated, and maintained to safely fulfill their intended function.
The assessment of the safety of a dam must be a continuing effort requiring periodic safety examinations
and evaluations throughout the life of the structure. The Division of Dam Safety recommends that relative
risk and hazard factors determined using the storage capacity of the reservoir; type of dam; height, age
and general condition of the dam; and present and anticipated downstream populations and development
be used in establishing the frequency of onsite inspections. The frequency of these onsite inspections of
a specific dam, once established, should be updated as the above factors change. Based on the high
priority placed on previously identified deficiencies, some dams will require regular examinations on a
more frequent basis than others.
The purpose of a safety evaluation is to determine the status of a dam relative to its structural and
operational safety. The evaluation should identify problems and recommend either remedial repairs,
operational restrictions and/or modifications, or analyses and studies to determine solutions to the
problems.
A minimum prerequisite for any dam owner/operator who desires a better understanding of dams and
dam safety is familiarity with the following:



Basic terminology and common dam elements
Means by which dams fail
Devices with which dams can be monitored
The remainder of the information contained in Section 1.0 of this manual, along with the Glossary of
Terms contained in Appendix D, is intended to cover the items described above.
1.2
Common Dam Elements
The common elements of a typical dam are illustrated in the figure below.
FIGURE 1
-2-
1.3
Types of Failures
Dam failures are usually the result of either poor design, improper construction, improper operation,
inadequate maintenance, or a combination of these factors. The manner in which a dam fails and the
particular causes of failure are usually varied, multiple, complex and interrelated. However, failure modes
may be divided into the following three general categories: a) hydraulic failures; b) seepage failures; and
c) structural failures. These failure modes are defined below.
a. Hydraulic. Hydraulic failures are those resulting from the erosive action of the uncontrolled flow of
water adjacent to the dam and its foundation. Earth dams are particularly susceptible to hydraulic failure
since earth erodes when subjected to flows at relatively low gradients.
b. Seepage. Seepage must be controlled in velocity and amount. Seepage may occur both through the
dam as well as under and around the dam in the foundation and abutment materials. Seepage, if
uncontrolled, can erode material starting at the downstream slope or foundation and working back toward
the upstream slope to form a "pipe" which often leads to a complete failure of the structure. This
phenomenon, known as "piping", is defined as the progressive development of internal erosion. It can
also contribute to destabilizing movements of the embankment such as slides or sloughs.
-3-
c. Structural. Structural failures involve the rupture of the dam and/or its foundation. This is a
particularly important hazard on large dams and on dams built of low strength clays, silts and other
materials such as slag and fly ash.
1.4
Monitoring Devices
Various devices exist that can be used to monitor the physical changes occurring within the dam over time.
These devices provide a quantitative measure of the changes. Thus, when used in combination with visual
inspections, a more complete assessment of the condition of a dam may be made.
The need for monitoring devices during the design and/or the construction phases depends upon the hazard
potential classification of the dam. During the life of a dam, as changes occur, it may become necessary to
add one or more types of monitoring devices. The types of monitoring devices required and their location
should be determined by a qualified professional engineer, and be in compliance with Division of Dam Safety
requirements.
The installation of instrumentation after a dam has been in operation is usually in response to a need for data
to assess the safety of the dam, stemming from concern about conditions observed during a visual
inspection. The Division of Dam Safety may require installation of monitoring devices based upon its own
evaluation of the annual inspection reports submitted by the owner's engineer.
The more common monitoring devices are presented in Table 1.0.
For easy reference the remainder of this manual has been divided into three main sections as follows:
Section 2.0 Dam Inspection - This section provides step-by-step procedures for dam inspections.
Included are: 1) a checklist of equipment recommended for an efficient and thorough inspection of the
facility; 2) a recommended inspection sequence; and 3) a partial list of problems and conditions that
may be observed during a typical dam inspection.
Section 3.0 Dam Maintenance - This section covers the areas of required maintenance for a typical dam.
Included are discussions of various specific maintenance items along with a recommended maintenance
schedule.
Section 4.0 Dam Operation - This section provides guidelines for the development of an adequate
operation plan. In addition, the section defines the basic elements of an effective emergency warning
system including a surveillance and warning plan, and an evacuation plan.
Finally, an index is provided at the back of this manual (see Appendix E) to aid the user in quickly locating
any subject matter contained herein.
-4-
Table 1.0
COMMON MONITORING DEVICES
Device
1.
Survey Monuments
or
Permanent Points
Purpose
Comments
Provides set points (to be surveyed
during the dam's life) from which
the displacements that the dam
undergoes may be measured.
The monuments should be installed
so as to provide enough survey points
from which vertical, horizontal, and
angul ar dis pl ac em ents m a y b e
measured.
FIGURE 2
2.
Inclinometers
Used
to
monitor
internal
displacements of the embankment
and/or its foundation.
The system consists of a special casing
with grooves on the inside at the
quarter points. The casing is installed in
a drilled hole and backfilled with
material selected by the engineer. Then
an instrument is used to traverse the
length of the casing and determine its
profile in two perpendicular directions.
All readings are compared with the
initial profile to determine if changes have
occurred.
FIGURE 3
3.
Observation Wells
Used to measure the height of the
water surface in the embankment at
the location of the well.
-5-
Observation wells should be installed
along the cross section of the dam so
as to provide a clear picture of the
water surface through the dam, i.e.,
more than one well across a section
should be installed.
4.
Weir
Measures the quantity of leakage
occurring through the embankment
and/or foundation.
-6-
When measurable quantities of flow
are occurring through the foundation
and/or embankment, a system of
drainage ditches should be excavated
and the flow from the various seeps
collected and diverted into a channel
across which the weir has been constructed. The dimensions and the
depth of water flowing over it are used
to calculate the quantity of flow.
SECTION 2.0
DAM INSPECTION
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SECTION 2.0 — DAM INSPECTION
2.1
General
a. Introduction. The purpose of this section is to provide a dam owner/operator with a simple and
systematic method for inspecting a dam. Simple because it involves a "learn as you go" procedure. The
easy to follow steps allow for any dam owner/operator to custom fit the system to his particular facility.
The method emphasizes techniques of observation rather than evaluation, which is more properly the
responsibility of experienced professionals.
The relationship of a dam to its owner should be, but often is not, similar to the relationship of a home and
its owner. Many homeowners do not fully understand the intricacies of home design and construction, or
the workings of a particular item like the plumbing. This, similarly, is very often the case for a dam
owner/operator. However, by living day after day in his home, the homeowner gains a feel for it. He learns
its peculiarities and is aware of unusual developments. Continual observation allows the home owner to
recognize a problem and enables him to sense how much time he has before he must make repairs. The
dam owner/operator must approach his dam in the same manner. The key is getting to know the facility.
The wise dam owner/operator knows his dam well even though he may not thoroughly understand it. He
can recognize a physical condition that has changed or is developing. He can sense when equipment is
not operating properly. Over time, the dam owner/operator, like the homeowner, gains a feel for the
condition of his property.
Dam owner/operators, however, must go a step further than homeowners. A homeowner may keep
mental notes whereas a dam owner/operator must maintain records. A major problem in a home will likely
only affect the lives of the homeowner and his family. Dam problems have the potential to affect the lives
of all of the families located in the floodplain downstream. In order to protect himself and his downstream
neighbors, the dam owner/operator needs to write down his observations, take photographs, make
sketches, and refer to this manual to gain a better understanding of what he sees.
Overall the dam owner/operator, in time, learns how to take care of the dam. Through experience he
understands how his dam is supposed to appear. Very often the existence of a problem is not as
important as the rate of development or change in its condition. Continuous observation and recording of
conditions is the best means for maintaining familiarity with the dam. In this way, the dam owner/operator
becomes an effective observer and serves to protect himself, his investment, and his downstream
neighbors.
b. Pennsylvania Inspection Requirements. The owner of a dam in Pennsylvania must inspect the
facility at least once every three months according to the rules and regulations contained in Chapter 105
(Reference 22, Appendix C). In addition, all dams with Category 1 or 2 High-Hazard Potential
Classification must be inspected annually by a registered professional engineer experienced in dam
design, construction and inspection. Annual reports certified by the engineer regarding the condition of
the dam must be submitted to the Division of Dam Safety on or before December 31 of each year. More
frequent reports may be required by the Division of Dam Safety if, at its discretion, conditions indicate
-8-
such reports are necessary to assure adequate protection of health, safety and property (see Inspection
Checklists in Appendix B).
For additional information regarding Dam Safety Regulations in Pennsylvania, see References 21 and 22
identified in Appendix C.
c. Inspection Preparation.
1. Review Existing Data. Design reports, construction drawings, correspondence, hand-written notes,
photographs, sketches, etc. are likely the most overlooked resource available to a dam owner/operator.
These records provide insights into the history of the facility and are often invaluable. The volume of
available data varies greatly from dam to dam. Information has often been stored carelessly and, in many
cases, has been destroyed by fire or flood. It is important that the dam owner/operator establish an
orderly information file on his dam and maintain all available data in a secure location. The Division of
Dam Safety maintains data files on all dams that have received permits. It is recommended that dam
owners/operators contact the Division of Dam Safety for further information regarding their dams.
An important part of the dam inspection method is a thorough review of existing data. Typically the dam
owner/operator should review his entire file a day or two prior to the inspection in order to note past
conditions, especially the location of previously observed deficiencies.
2. Gather Appropriate Inspection Equipment. The degree of difficulty in performing any task depends
a lot on whether or not one is outfitted with the proper equipment and tools. The following are lists of
required and recommended inspection equipment. The required items represent equipment pieces
without which a proper inspection simply cannot be performed. The recommended items should help the
dam inspector achieve even better results. Through experience the inspector will learn what tools he
really needs to adequately inspect his facility.
a) Required Inspection Equipment:

CLIPBOARD and INSPECTION CHECKLIST — Clipboard provides a solid writing surface.
Inspection checklist serves as a reminder to inspect all important areas. An example is presented
at the end of this section.

NOTEBOOK and PENCIL — It is very important to write down observations at the time they are
made. This reduces mistakes and the need to return to the area to refresh the inspector's
memory.
-9-

STANDARD SIX-FOOT COLLAPSIBLE RULE — This provides a means for making rough
measurements at the dam. Measurements are extremely useful and should be taken whenever
possible.
b) Recommended Inspection Equipment.

CAMERA — Photographs provide a reliable record of observed field conditions. They can be
valuable in comparing past and present configurations. An inexpensive model usually takes
pictures good enough for inspection records.

TAPE RECORDER — This can be utilized to supplement hand-written notes. It allows the
inspector to record a greater volume of observations.

HANDLEVEL — This is needed to accurately locate areas of interest and to determine
embankment heights and slopes.

PROBE — A probe can provide information on conditions below the surface, such as the depth
and softness of a saturated area. Any stiff light rod with a pointed tip and of sufficient strength to
penetrate soil will do.

HARD HAT — A hard hat is recommended for inspecting large outlets or working in construction
areas.

POCKET TAPE — Many descriptions are not accurate enough when estimated, paced, or
roughly measured with a six-foot collapsible rule. The pocket tape provides accurate
measurements which allow meaningful comparisons to be made.

FLASHLIGHT — The interior of an outlet in a small dam can often be inspected adequately
without crawling through it by shining a good flashlight or fluorescent light into the outlet and
observing conditions.

CONTAINER AND TIMER — These are used to make fairly accurate measurements of seepage
rates. Establishing the time it takes the seepage flow to fill the container, such as a gallon bucket,
enables the inspector to calculate the number of gallons per minute of flow. Various container
sizes may be required, depending on the flow rates.

STAKES AND FLAGGING TAPE — These are used to mark areas requiring future attention and
to stake the limits of existing conditions, such as cracks and wet areas, to allow future
comparison.

WATERTIGHT BOOTS — These are often required when inspecting various areas of the dam
site where standing water is present.

SHOVEL — A long-handled shovel is useful in clearing drain outfalls, removing debris and
locating monitoring points.

ROCK HAMMER — Questionable-looking riprap or concrete can be checked for soundness with
a rock hammer. However, care must be taken not to break through thin spots or cause
unnecessary damage.

BONKER — The condition of support material behind concrete or asphalt faced dams generally
cannot be determined by observing the surface of facing alone. Conditions below the surface may
be determined by the sound produced when the surface facing material is firmly tapped. Facing
material fully supported by fill material produces a "clink" or "bink" sound, whereas facing material
that is over a void or hole in the facing produces a "clonk" or "bonk" sound. The bonker can be
- 10 -
made of 1-inch hardwood dowel with a metal tip firmly affixed to the tapping end. A rubber shoe
like those on some furniture legs is recommended for the other end to allow the bonker to be
used as a walking aid on steep, slippery slopes.

BINOCULARS — These are useful for inspecting limited access areas especially on concrete
dams.
3. Follow a Predetermined Inspection Sequence. The purpose of preparing an inspection route in
advance is to assure that every part of the dam will be observed. The route is repeated as often as
necessary to insure that the inspector has viewed every square foot of the facility.
A productive sequence of inspection that has been used with favorable results is as follows:
i.
CREST — Walk across the crest from abutment to abutment.
ii.
UPSTREAM SLOPE — Walk across the upstream slope in an up and down or zig-zag pattern
from abutment to abutment.
iii. DOWNSTREAM SLOPE — Walk across the downstream slope in an up and down or zig-zag pattern from abutment to abutment.
iv. EMBANKMENT—ABUTMENT CONTACTS — Walk the entire length of the embankmentabutment contacts.
v.
OUTLET CONDUIT — Observe all accessible features of the outlet conduit.
vi. SPILLWAY — Walk along the entire length of the spillway in a back and forth manner.
vii. ABUTMENTS — Traverse abutments in a practical manner so as to gain a general feel for the
conditions which exist along the valley sidewalls.
viii. DOWNSTREAM CHANNEL — Travel the route of the stream below the dam to maintain familiarity with locations, of residences and property which could be affected by dam failure.
ix. RESERVOIR SLOPES — Scout the reservoir perimeter in an effort to develop an overall
familiarity with its conditions.
Following a specific predetermined route will lessen the chance of overlooking an important condition.
Repeating the same route each inspection will aid in the development of consistent records.
2.2 Inspection Items
The following section contains a description of the most common deficiencies that might be observed
during a dam inspection.
The information that follows should not be construed as an all-encompassing last word on the problems
which may be encountered. In particular, the probable causes and possible harmful effects that are listed
for each condition are not intended to cover all possibilities. If the dam inspector encounters a condition
which he feels is not addressed in this section or any condition, the severity of which he questions, he
should immediately contact the Division of Dam Safety (refer to telephone numbers listed in Appendix A).
- 11 -
a. EMBANKMENT.
The information contained in this section is organized in a manner intended to allow for easy use and
quick reference. Match the condition observed during the embankment inspection with one of the conditions presented in this section. As an example, a typical condition that could be encountered is presented
as shown below.
Excess Vegetation
Probable Causes: 7 (See Table 2.0)
Possible Harmful Effects: 10, 11 (See Table 2.1)
Recommended Actions: 20, 21 (See Table 2.2)
Table 2.0
PROBABLE CAUSES OF EMBANKMENT CONDITIONS
1.
Embankment and/or foundation movement.
2.
Internal and/or external erosion of material.
3.
Soil weakening due to water infiltration.
4.
Unusual increase in the loads on the dam (for example, due to: earthquake, high pool level, rapid
lowering of pool level, additional dead weight on embankment).
5.
Rodent activity.
6.
Deterioration due to weathering.
7.
Inadequate maintenance.
8.
Soil shrinkage due to moisture loss.
9.
Improper construction and/or inadequate design.
10.
Vehicle traffic.
11.
Locally steep slope.
12.
Wave action.
13.
Vandalism.
14.
Developed seepage path reaching external surface.
15.
Retained rainfall/snowmelt on surface.
16.
Natural seeding.
17.
Change in seed type during initial postconstruction seeding.
18.
Leaking outlet conduit.
- 12 -
Table 2.1
POSSIBLE HARMFUL EFFECTS OF EMBANKMENT CONDITIONS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Exposes interior portion of embankment directly to the elements, particularly precipitation, which
may lead to a more deteriorated condition.
May create a local area of inadequate strength within the embankment which could lead to future
movement.
May be indicative of unstable conditions. Could lead to failure.
Reduces available embankment cross section, thus decreasing resistance to movement.
Provides a potential path which may lead to erosive seepage.
Reduces available freeboard.
Represents an area particularly susceptible to erosion damage which can lead to dam failure.
Uncontrolled internal erosion which can lead to dam failure.
Could become an area susceptible to local movement if due to wet conditions.
Obscures visual observation.
Deterioration of roots may leave voids which may lead to erosive seepage.
Can lead to rapid erosion of abutment and/or evacuation of the reservoir.
Can lead to movement and affect the stability of the dam.
Provides an area for water to accumulate which could result in soil softening and create an area of
inadequate strength within the embankment.
Table 2.2
RECOMMENDED ACTIONS FOR EMBANKMENT CONDITIONS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
Photograph condition.
Carefully inspect and record the location and physical dimensions of the conditions.
Place stakes at the limits of the condition and monitor frequently to detect any changes in
observed conditions.
If condition was never previously observed, bring condition to the attention of an engineer during
the next annual inspection.
If condition was observed during a previous inspection and brought to the attention of a qualified
engineer, note any changes in its physical dimensions.
If condition appears to be unusual or inconsistent with previous observations, immediately contact
the Division of Dam Safety.
If condition has never been previously observed, contact the Division of Dam Safety immediately
for further consultation and possible action.
Contact the Division of Dam Safety immediately for further consultation and possible action.
Regrade to provide for uniform drainage.
Fill low areas with compacted soil.
Apply gravel layer or other suitable roadbase to accommodate traffic.
Repair erosion if necessary.
Replace riprap.
Consult a qualified engineer to make recommendations for remedial measures.
Repair by replacing eroded material with compacted fill.
Apply non-erodible material (rock, concrete, asphalt, etc.) for protection against future erosion.
Record flow rate if possible. Frequent measurements or estimates may be necessary if flow rate is
changing rapidly.
Note any evidence of muddy flow.
Post warning signs prohibiting vehicular traffic along slope and/or restrict access.
Control excessive brush through regular routine maintenance.
Remove large trees under the direction of a qualified engineer.
- 13 -
EMBANKMENT CREST
Thin Random Cracking
Longitudinal and/or Transverse Cracks
FIGURE 4
Probable Causes: 8
Possible Harmful Effects: 1
Recommended Actions: 1, 2, 3, 4, 5, 6
Probable Causes: 1, 2, 4
Possible Harmful Effects: 1, 2, 5
Recommended Actions: 1, 2, 3, 5, 6, 7
Excessive Vegetation
Crest Arching or Bowing
Probable Causes: 7
Possible Harmful Effects: 10, 11
Recommended Actions: 20, 21
Probable Causes: 1, 3, 4.
Possible Harmful Effects: 3
Recommended Actions: 1, 2, 3, 5, 6, 7
- 14 -
EMBANKMENT CREST
Low Area in Dam Crest
Sinkhole or Animal Burrow
FIGURE 5
FIGURE 6
Probable Causes: 1, 2, 9
Possible Harmful Effects: 3, 7, 14
Recommended Actions: 1, 2, 3, 5, 6, 7
Probable Causes: 2, 5
Possible Harmful Effects: 1, 3
Recommended Actions: 1, 2, 3, 5, 6, 7
Ruts or Puddling on Dam Crest
Probable Causes: 7, 9, 10
Possible Harmful Effects: 1, 7, 14
Recommended Actions: 9, 10, 11
- 15 -
UPSTREAM EMBANKMENT SLOPE
Slide, Slough, or Scarp
Broken Down or Missing Riprap
Probable Causes: 1, 3, 4, 11, 12
Possible Harmful Effects: 1, 3, 4
Recommended Actions: 1, 2, 3, 5, 6, 7
Probable Causes: 11, 12, 13
Possible Harmful Effects: 7
Recommended Actions: 1, 12, 13
Erosion Behind Poorly Graded Riprap
Deteriorated Slope Protection
(concrete, asphalt, other material)
FIGURE 7
Probable Causes: 12
Possible Harmful Effects: 7
Recommended Actions: 1, 14
Probable Causes: 6, 9, 12
Possible Harmful Effects: 7
Recommended Actions: 1, 14
- 16 -
UPSTREAM EMBANKMENT SLOPE
Sinkhole or Animal Burrow
Whirlpool in Reservoir
FIGURE 8
Probable Causes: 2, 5
Possible Harmful Effects: 1, 3
Recommended Actions: 1, 2, 3, 5, 6, 7
Probable Causes: 2, 18
Possible Harmful Effects: 3, 8
Recommended Actions: 1, 8
Erosion at Embankment-Abutment Contact
Excessive Vegetation
FIGURE 9
Probable Causes: 9
Possible Harmful Effects: 7
Recommended Actions: 1, 15, 16
Probable Causes: 7
Possible Harmful Effects: 10, 11
Recommended Actions: 20, 21
- 17 -
DOWNSTREAM EMBANKMENT SLOPE
Clear Seepage
Muddy Seepage
Probable Causes: 14
Possible Harmful Effects: 2, 8
Recommended Actions: 1, 2, 3, 5, 6, 7, 17, 18
Probable Causes: 2, 14
Possible Harmful Effects: 2, 3, 8
Recommended Actions: 1, 2, 3, 8, 17
Wet Areas (no measurable flow)
Marked Change in Vegetation
FIGURE 10
Probable Causes: 14, 15
Possible Harmful Effects: 3
Recommended Actions: 1, 2, 3, 5, 6, 7
Probable Causes: 14, 15, 16, 17
Possible Harmful Effects: 9
Recommended Actions: 1, 2, 3, 5, 6, 7
- 18 -
DOWNSTREAM EMBANKMENT SLOPE
Sinkhole or Animal Burrow
Slide, Slough, or Scarp
Probable Causes: 2, 5
Possible Harmful Effects: 1, 3
Recommended Actions: 1, 2, 3, 5, 6, 7
Probable Causes: 1, 3, 4, 11
Possible Harmful Effects: 1, 3, 4, 7
Recommended Actions: 1, 2, 3, 5, 6, 7
Erosion at Embankment-Abutment Contact
Bulging
FIGURE 11
FIGURE 12
Probable Causes: 9
Possible Harmful Effects: 7
Recommended Actions: 1, 15, 16
Probable Causes: 1
Possible Harmful Effects: 3
Recommended Actions: 1, 2, 3, 5, 6, 7
- 19 -
DOWNSTREAM EMBANKMENT SLOPE
Erosion
Excessive Vegetation
Probable Causes: 6, 10
Possible Harmful Effects: 7
Recommended Actions: 1, 15, 19
Probable Causes: 7
Possible Harmful Effects: 10, 11
Recommended Actions: 20, 21
ABUTMENTS AND FOUNDATION
Seepage Water Exiting as a Boil in the Foundation
Trampoline Effect in Large Soggy Area
FIGURE 13
Probable Causes: 2, 14
Possible Harmful Effects: 3, 8
Recommended Actions: 1, 2, 3, 8
FIGURE 14
Probable Causes: 14
Possible Harmful Effects: 3
Recommended Actions: 1, 2, 3, 8
Leakage from Abutments Beyond
the Dam
Probable Causes: 14
Possible Harmful Effects: 12, 13
Recommended Actions: 1, 2, 3, 5, 6,
7, 17, 18
- 20 -
ERODIBLE CHANNELS (Earth or Rock Cuts through Abutment)
CONDITION OBSERVED
SLIDE, SLOUGH OR SCARP
PROBABLE CAUSES
AND POSSIBLE
HARMFUL EFFECTS
RECOMMENDED ACTION
PROBABLE CAUSES:
1. Photograph condition.
1. Locally steep side slope.
2. Repair damaged area by replacing
eroded material with compacted
fill.
2. Discharge flow has eroded toe of
slope.
POSSIBLE HARMFUL EFFECTS:
1. Reduces open cross section of
channel
and
thereby
reduces
available spillway discharge capacity.
Inadequate spillway capacity can
lead to embankment overtopping and
result in dam failure.
3. Protect area against future erosion
by installing suitable rock riprap.
Revegetate area if appropriate.
4. Bring condition to the attention of
the engineer during next annual
inspection.
2. Unabated
erosion
in
earthen
spillways can lead to larger slides
within the abutment that can eventually affect the stability of the
embankment.
FIGURE 16
EROSION CHANNELS
PROBABLE CAUSES:
1. Surface
runoff
from
intense
rainstorms or flow from spillway carries surface material down the
slope, resulting in continuous
troughs.
2. Bicycle or livestock traffic create
gullies where flow concentrates.
POSSIBLE HARMFUL EFFECTS:
1. Unabated erosion can lead to
slides, slumps or slips which can
result in reduced spillway capacity.
Inadequate spillway capacity can
lead to embankment overtopping
and result in dam failure.
1. Photograph condition.
2. Repair damaged areas by replacing
eroded
material
with
compacted fill.
3. Protect areas against future erosion by installing suitable rock
riprap.
Revegetate
area
if
appropriate.
4. Bring condition to the attention of
the engineer during next annual
inspection.
FIGURE 17
EXCESSIVE VEGETATION OR DEBRIS
IN CHANNEL
PROBABLE CAUSES:
1. Inadequate maintenance.
2. Deposition of debris after flooding.
1. Provide
regular
maintenance
routine
2. Inspect after flooding events and
maintain as required.
- 21 -
POSSIBLE HARMFUL EFFECTS:
1. Obscures visual observation.
2. Obstructs spillway discharge and
reduces available spillway capacity.
Inadequate spillway capacity can
lead to embankment overtopping
and result in dam failure
FIGURE 18
NON—ERODIBLE CHANNELS (Lined with Concrete, Asphalt, Masonry, Etc.)
CONDITION OBSERVED
WALL DISPLACEMENT OR
MISALIGNMENT
PROBABLE CAUSES
AND POSSIBLE
HARMFUL EFFECT
RECOMMENDED ACTION
PROBABLE CAUSES:
1. Poor
workmanship
construction.
1. Photograph condition.
during
2. Uneven settlement of foundation.
2. Contact a qualified engineer for
consultation and development of.
remedial actions.
3. Excessive earth and water pressure
on channel sidewalls.
4. Poor design.
FIGURE 19
POSSIBLE HARMFUL EFFECTS:
1. Minor displacement can create
eddies and turbulence in the flow,
and precipitate erosion and/or wall
damage.
2. Major displacement can lead to
severe cracks or slab movement
and eventually result in failure of the
spillway structure.
OPEN OR DISPLACED JOINTS
PROBABLE CAUSES:
1. Poor
workmanship
construction.
during
2. Excessive and/or uneven settlement
of foundation.
3. Sliding of concrete slab.
4. Deteriorated sealant.
FIGURE 20
POSSIBLE HARMFUL EFFECTS:
1. Joint openings allow water to enter
and erode material beneath the
concrete which can lead to
weakened foundation support and
eventual failure of the spillway
structure.
- 22 -
1. Photograph condition.
2. Contact a qualified engineer for
consultation and development of
remedial actions.
END OF SPILLWAY
CHUTE UNDERCUT
PROBABLE CAUSES:
1. Poor design and/or construction.
1. Photograph condition.
2. Inadequate erosion protection.
2. Dewater affected area. Replace
eroded material with compacted
backfill. Provide suitable rock
riprap to protect against future
erosion.
POSSIBLE HARMFUL EFFECTS:
1. Can lead to extensive undermining
of foundation and eventually result
in failure of the spillway structure.
2. Unabated erosion can lead to instability of adjacent portions of the
embankment.
SEEPAGE FROM A CONCRETE JOINT PROBABLE CAUSES:
OR CRACK
1. Insufficient or clogged weep holes
are causing water collected behind
spillway to exit by whatever route
available.
EXCESSIVE VEGETATION
OR DEBRIS IN CHANNEL
3. Contact a qualified engineer for
consultation to assess need for additional remedial measures.
1. Photograph condition.
2. Clean all weep holes and drain
outfalls.
POSSIBLE HARMFUL EFFECTS:
3. Check areas behind walls for
ponding of surface water.
1. Excess water pressure can lead to
instability of the spillway structure.
Failure of the spillway structure can
lead to dam failure.
4. If condition persists a qualified
engineer should inspect the condition and recommend further
actions to be taken.
PROBABLE CAUSES:
1. Inadequate maintenance.
2. Deposition of debris after flooding.
POSSIBLE HARMFUL EFFECTS:
1. Obscures visual observation.
2. Obstructs spillway discharge and
reduces available spillway capacity.
Inadequate spillway capacity can
lead to embankment overtopping
and result in dam failure.
FIGURE 21
- 23 -
1. Provide
regular
maintenance.
routine
2. Inspect after flooding events and
maintain as required.
c. OUTLET WORKS
CONDITION OBSERVED
OUTLET PIPE DAMAGE
PROBABLE CAUSES AND POSSIBLE
HARMFUL EFFECTS
PROBABLE CAUSES:
1. Settlement
foundation.
of
embankment
All Conditions:
1. Photograph condition.
2. Check for evidence of water
either entering or exiting pipe at
crack/hole/etc.
2. Corrosion (metal pipe).
3. Erosion (concrete pipe).
4. Cavitation
5. Poor design and/or construction.
POSSIBLE HARMFUL EFFECTS:
1. Provide opening for flow to exit
conduit. Could lead to erosion of
embankment materials and result in
failure of dam.
FIGURE 22
FIGURE 22
VALVE LEAKAGE
RECOMMENDED ACTION
3. Repair damage. Outlet conduit
should not be used until repairs are
completed. If problem is the result
of cavitation, discuss possibility of
installing an air vent with a qualified
engineer.
4. Recheck frequently to insure that
repairs have been effective.
PROBABLE CAUSES:
A. Debris Stuck Under Gate
1. Due to ineffective or damaged trash
rack
POSSIBLE HARMFUL EFFECTS
1. Raise and lower gate slowly until
debris is loosened and floats past
valve. When reservoir is lowered,
repair or replace trash rack.
1. Gate will not close. Gate or stem
may be damaged in effort to close
gate.
FIGURE 23
PROBABLE CAUSES
B. Cracked Gate Leaf
1. Due to ice action, rust, impact,
vibration, or stress resulting from
attempting to close gate when it is
jammed.
1. Use valve only in fully open or
closed position. Minimize use of
valve until leaf can be repaired or
replaced.
FIGURE 24
POSSIBLE HARMFUL EFFECTS:
1. Gate leaf may
causing
rapid
reservoir.
fail completely
drawdown
of
PROBABLE CAUSES:
C. Damaged Gate Seat or Guides
FIGURE 25
1. Due to rust, erosion,
vibration, or wear.
- 24 -
cavitation,
1. Minimize use of valve until
guides/seats can be repaired. If
cavitation appears to be cause
check to see if air vent pipe exists
and is unobstructed.
POSSIBLE HARMFUL EFFECTS:
1. Leakage and loss of support for gate
leaf.
2. Gate may bind in guides and
become inoperable.
DAMAGE TO CONTROL WORKS
PROBABLE CAUSES:
A. Broken Block Support
1. Concrete deterioration
2. Excessive force exerted on
control stem by attempting to
open gate when it was jammed.
B. Bent/Broken Control Stem
1. Rust.
2. Excess force used to open or
close gate.
3. Excessive ice pressures.
FIGURE 26
C. Broken/Missing Stem Guides
1. Rust.
2. Inadequate lubrication
3. Excess force used to open or close
gate when it was jammed.
POSSIBLE HARMFUL EFFECTS
A. Broken Block Support
1. Causes control support block to tilt;
control stem may bind.
2. Control headworks may settle.
3. Gate may not open all the way.
4. Support block may fail completely
leaving outlet inoperable.
B. Bent/Broken Control Stem.
1. Outlet is inoperable.
C. Broken/Missing Stem Guides
1. Loss of support for control stem.
Stem may buckle and break under
normal use.
- 25 -
1. Photograph condition.
2. Repair damage (may require
assistance of a qualified engineer).
Minimize use of systems until
repairs are completed.
SEEPAGE WATER EXITING FROM A
POINT ADJACENT TO THE OUTLET
PROBABLE CAUSES:
1. An opening in the outlet pipe.
1. Photograph condition.
2. A path for flow has developed along
the outside of the outlet pipe.
2. Determine if leakage water is carrying soil particles.
POSSIBLE HARMFUL EFFECTS:
1. Continued flows can lead to rapid
erosion of embankment materials
and failure of the dam.
3. Measure quantity of flow.
4. Close outlet valve and determine
whether or not flow decreases or
stops.
5. Contact the Division of Dam Safety
immediately for further consultation and possible action.
DISCHARGES FROM OUTLET
ERODING TOE OF DAM
PROBABLE CAUSES:
1. Outlet pipe does not extend far
enough downstream of embankment toe.
2. Insufficient slope protection and/or
means of dissipating the energy of
flow at the point of release.
1. Photograph condition.
2. Extend pipe beyond toe (use a
pipe of same size and material,
and form watertight connection to
existing conduit.)
3. Repair damaged area by replacing
eroded material with compacted
fill.
POSSIBLE HARMFUL EFFECTS:
FIGURE 27
DETERIORATION AT OUTLET
DISCHARGE STRUCTURE
4. Protect area with
suitable bedding.
1. Unabated erosion can lead to embankment instability and result in
failure of the dam.
PROBABLE CAUSES:
1. Photograph condition.
1. Weathering.
2. Repair damage.
2. Undermining of foundation.
3. Excessive pressures exerted on the
sidewalls of the structure.
POSSIBLE HARMFUL EFFECTS:
1. Can lead to failure of the outlet
discharge structure that serves to
protect the downstream embankment toe against harmful erosion.
FIGURE 28
- 26 -
riprap
over
d. MISCELLANEOUS
RESERVOIR
CONDITION OBSERVED
UNSTABLE RESERVOIR SLOPES
PROBABLE CAUSES AND POSSIBLE
HARMFUL EFFECTS
RECOMMENDED ACTION
PROBABLE CAUSES:
1. Area of ancient slide activity.
1. Photograph condition.
2. Removal of support material from
base of slope.
2. Contact the Division of Dam Safety
immediately for further consultation and possible action.
3. A change in groundwater activity.
POSSIBLE HARMFUL EFFECTS:
1. Can lead to massive slides involving
large volumes of earth and rock.
This has been known to displace
enough reservoir water to cause the
dam to overtop and fail.
MONITORING DEVICES
CONDITION OBSERVED
INOPERABLE OR DAMAGED
INSTRUMENTATION
PROBABLE CAUSES AND POSSIBLE
HARMFUL EFFECTS
PROBABLE CAUSES:
1. Improper installation.
2. Movements
monitored.
in
3. Carelessness
maintenance.
the
1. Repair
area
during
being
routine
4. Neglect.
5. Vandalism.
6. Excessive wear.
FIGURE 29
POSSIBLE HARMFUL EFFECTS:
1. Loss of important data needed to
assess whether or not dam is functioning within safe guidelines.
- 27 -
RECOMMENDED ACTION
existing
instruments
if
possible.
2. Consult with a qualified engineer
to determine the need for
replacements.
METALWORK
CONDITION OBSERVED
GENERAL DETERIORATION:
CORROSION, HOLES, ETC.
PROBABLE CAUSES AND POSSIBLE
HARMFUL EFFECTS
RECOMMENDED ACTION
PROBABLE CAUSES:
1. Excessive
exposure.
weathering
and
1. Photograph condition.
2. Inadequate maintenance.
2. Scrape and clean, if necessary, to
fully assess extent of deterioration.
POSSIBLE HARMFUL EFFECTS:
3. Repair or replace as required.
1. Depends on the importance and
function of the item in question.
Should be assessed on an item-byitem basis.
STRUCTURAL DEFICIENCIES:
PROBABLE CAUSES:
CRACKS, LOOSE OR BROKEN JOINTS
1. Inadequate
design
and/or
OR CONNECTIONS (INCLUDING
construction.
METAL TO CONCRETE), BENT METAL,
ETC
2. Excessive stress through operation.
1. Photograph condition.
2. Repair or replace as required.
3. Wear and tear.
4. Vandalism.
5. Inadequate maintenance.
POSSIBLE HARMFUL EFFECTS:
1. Depends on the importance and
function of the item in question.
Should be assessed on an item-byitem basis.
CONCRETE AND CONCRETE DAMS
CONDITION OBSERVED
PROBABLE CAUSES AND POSSIBLE
HARMFUL EFFECTS
RECOMMENDED ACTION
CRACKING
PROBABLE CAUSES:
Longitudinal or Horizontal
1. Weathering and exposure.
1. Photograph condition.
2. Excessive stress
2. Have condition evaluated by a
qualified engineer
3. Inadequate concrete mix design.
3. Record
the
location
and
dimensions of the cracking for
comparison to future observations.
FIGURE 30
- 28 -
Transverse or Vertical
POSSIBLE HARMFUL EFFECTS:
1. Depends on the location, extent,
cause, length, width and depth of
cracking. Should be assessed on an
item-by-item basis.
FIGURE 31
Diagonal
Random
Pattern
FIGURE 32
FIGURE 33
FIGURE 34
CONDITION OBSERVED
PROBABLE CAUSES AND POSSIBLE
HARMFUL EFFECTS
RECOMMENDED ACTION
DETERIORATION
PROBABLE CAUSES:
Disintegration
1. Weathering and exposure.
1. Photograph condition.
2. Excessive stress.
2. Have condition evaluated by a
qualified engineer.
3. Inadequate concrete mix design.
3. Record the location and extent of
deterioration for comparison to
future observations.
4. Poor workmanship.
Distortion
POSSIBLE HARMFUL EFFECTS:
1. Depends on the location and extent
of deteriorated area. Should be
assessed on an item-by-item basis.
- 29 -
Scaling
Popout
Spalling
Exposed Reinforcing
Peeling
Efflorescence
LEAKAGE THROUGH JOINTS
PROBABLE CAUSES:
OR CRACKS
1. Deterioration of construction joint
has provided flow path.
1. Photograph condition.
2. Have condition evaluated by a
qualified engineer.
2. Excessive structural stress has
allowed
cracks
to
propagate
completely
through
structure
resulting in the development of a
flow path.
FIGURE 35
POSSIBLE HARMFUL EFFECTS:
1. May be indicative of internal erosion
which could lead to an unstable
condition. Depends on location of
condition and volume of flow.
2. Continually wet conditions promote
further deterioration.
MONOLITH MISALIGNMENT
PROBABLE CAUSES:
1. Excessive stress resulting from high
pool levels.
2. Foundation movement.
POSSIBLE HARMFUL EFFECTS:
1. Indicative of structural instability and
could lead to dam failure.
FIGURE 36
- 30 -
1. Photograph condition.
2. Have condition evaluated by a
qualified engineer.
2.3
Records
a.
Inspection Checklist. A convenient way of compiling inspection observations is by recording
them directly onto an inspection checklist. The checklist should be attached to a clipboard
and carried by the dam inspector as he traverses the entire structure. Sample checklists are
provided in Appendix B for convenience. Additional copies can be obtained by contacting
DEP (refer to Appendix A for address).
The following guidelines are recommended for properly utilizing the checklists.
1.
Fill out all basic data on the first page including name of dam, inspection date, weather
conditions, name(s) of inspector(s), pool level, DEP I. D. number, etc.
2. Briefly describe all observations. Attach sketches when appropriate.
3. If an item is not applicable, so indicate.
4. Record the fact if nothing is found to be wrong or damaged. Terms such as "good
condition" and "not observed" are often sufficient.
A good practice to follow along with filling out the inspection checklist is to draw a "field
sketch" of observed conditions. A typical field sketch is contained in Appendix B. The field
sketch is intended to supplement the information recorded on the inspection checklists;
however, it should be used as a substitute for clear and concise inspection checklists.
The DEP requires the dam owner to establish a permanent file to retain inspection records
including records of actions taken to correct conditions found in such inspections. Copies of
the records shall be provided to the department upon request. Without this file, the value of a
regular routine dam inspection is very short term. Only through establishment and
maintenance of records can evolutionary nature of a dam be comprehended and appreciated.
b.
Photographs. Inspection photographs can be vitally important because, over time, they
serve to provide a pictorial history of the evolving characteristics of a dam. The dam
owner/operator often finds pictures to be great money savers because they can illustrate that
some observed conditions (seepage, foundation movement, etc.) have existed for many
years and may have reached a state of safe equilibrium. With this knowledge, quick and
economical remedial actions can be developed and implemented. Without such photographs,
one would likely be forced to seek outside professional assistance to investigate the problem
prior to developing a repair scheme. Photographs should be dated on the back and provided
with brief descriptions. Another convenient method of compiling photographs is to paste or
tape the photographs to a sheet of paper and write or type the descriptions on the paper
adjacent to the photograph. A word of caution, however, is needed. Over time the tape or
paste may lose its adhesiveness. Thus, it is important to make sure each picture is properly
dated and described on the back.
Since the mid-1990’s, digital photography and word processing software have made it quite
convenient for a dam owner / operator to create a documented pictorial record of inspections
that can be stored in memory devices indefinitely. However, keeping printed copies on hand
of inspection reports with pictures is convenient for frequent review of past conditions. Digital
picture files stored on disk or other devices should be named with the dam, date, and subject
in the file name, rather than retaining the default naming by the camera.
c.
Monitoring Data. As previously indicated, it may become necessary to make measurements
of various items during the course of a dam inspection. This may include measurements of
seepage rates, spillway discharge rates, settlement, and for some dam owners, readings
from instruments such as piezometers. It is important that this data also be compiled in a
systematic manner and placed in a permanent file.
- 31 -
SECTION 3.0
DAM MAINTENANCE
- 32 -
SECTION 3.0 — DAM MAINTENANCE
3.1
Introduction
The value and importance of a regular program of routine maintenance cannot be overemphasized. The
Division of Dam Safety requires the dam owner to maintain the facility and all appurtenant structures in a
safe condition so that the facility may not endanger life; health, safety, or property located above or below
the facility. Routine maintenance is defined as minor maintenance, the performance of which neither
affects the normal operation of the facility or results in a modification of the original design and/or
specifications. The Division of Dam Safety requires the issuance of a written permit for any repairs or
maintenance involving modification of a dam from its original design and/or specifications and any repairs
or reconstruction involving a substantial portion of the structure.
An effective maintenance program has two main elements: 1) a listing of regular maintenance items or
tasks; and 2) a maintenance schedule.
3.2
Areas of Required Maintenance
In general, the listing of maintenance items or tasks can be broken into four major areas as follows:

embankment maintenance

spillway maintenance

outlet conduit maintenance

miscellaneous maintenance
The specific tasks that may be required in any of the above areas are discussed in detail later in this
section.
Maintenance is recognized as a continual day-to-day effort. Through establishment of a formal schedule,
many deficiencies which result from prolonged neglect can be averted. A maintenance schedule details
specific times when maintenance tasks will performed.
a.
Embankment. An effective program of regular routine embankment maintenance should
include, but not be limited to, the following items or tasks:

vegetation control

rodent control

minor earthwork and erosion repair

erosion protection
b.
Spillway. An effective program of regular routine spillway maintenance should include, but
not be limited to, the following items or tasks:

vegetation control

minor earthwork and erosion repair

erosion protection

concrete repair
- 33 -
c.
Outlet Conduit. An effective program of regular routine outlet conduit maintenance should
include, but not be limited to, the following items or tasks:

conduit internal maintenance

trash rack maintenance

mechanical-electrical-hydraulic maintenance

concrete repair
d.
Miscellaneous. An effective program of miscellaneous maintenance includes all remaining
areas, items, or devices not covered under the categories of embankment, spillway, or outlet conduit
maintenance. As an example, this should include, but not be limited to, the following items or tasks:
3.3.

operable equipment maintenance (mechanical, electrical, hydraulic)

monitoring instruments

security devices

access roads
Maintenance Items
a. Vegetation Control. The first maintenance requirement is to keep all portions of the dam clear
of unwanted vegetative growth. Excessive growth is harmful in the following ways:

It can obscure the view of the embankment and prevent a thorough inspection.

Weeds can discourage the growth of desirable grasses.

Some root systems can decay and rot, providing a tunnel for water to pass through and lead to
a piping failure.

Large trees could be uprooted during a storm and the resulting large hole left by the root
system could lead to breaching of the dam.

Root systems can cause the uplift of concrete slabs or structures.
In general, an effort should be made at least twice a year to cut down overgrowth and to keep vegetation
under control. Like trimming one's lawn, the more frequently the dam owner/operator attends to the
vegetation control needs of the dam, the easier it is. Thus, there may be an advantage to tending to this
need often so that the chore never becomes too large to tackle without additional assistance and
equipment.
b. Rodent Control. Rodents such as groundhogs, muskrats, and beavers are naturally attracted
to areas of ponded water such as dams and reservoirs. Earth dams are most susceptible to problems
caused by these rodents. As a matter of fact, beavers can cause problems for any type of dam
construction. Table 3.0 presents a description of each rodent, potential problems caused by each,
recommended methods of control, and measures to repair the damage.
- 34 -
Under Pennsylvania law the control or extermination of groundhogs, muskrats and beavers is
subject to certain restrictions. Prior to taking any action against these rodents the dam owner/operator is
advised to contact the Wildlife Conservation Officer through a regional office of the Pennsylvania Game
Commission. Information is available on the Game Commission’s website at www.pgc.state.pa.us.
Table 3.0
RODENTS AND RODENT CONTROLS
Rodent
Methods of
Control
Groundhog or
Woodchuck
Problem
Remedial Measures
Fumigation or
Shooting
Groundhogs usually burrow into
the downstream embankment
slope forming tunnels and dens
inside the dam above the
phreatic surface. These
passageways not only decrease
the stability of the dam, but could
become conduits during flooding
periods leading to breaching of
the dam.
Fill burrow with slurry mixture of
earth (90 percent) and cement
(10 percent) by pouring through
large diameter pipe. Outer
surface should then be covered
with well-compacted earth and
vegetation reestablished.
Muskrat
Trapping
Muskrats usually burrow into the
upstream embankment slope.
Their burrows begin six to
18 inches below the water
surface and penetrate the
embankment on an upward slant.
At distances up to 15 feet from
the entrance, a dry chamber may
be hollowed out above the water
level. Once a muskrat den is
occupied, a rise in the water level
will cause the muskrat to dig
farther and higher to excavate a
new dry chamber. Damage (and
the potential for problems) is
compounded where groundhogs
or other burrowing animals
construct their dens in the
embankment opposite muskrat
dens.
Same as for groundhog burrows.
Beaver
Trapping
Beavers often build dens along
the upstream embankment slope
and into the dam. They also have
been known to block spillways
with their own dams.
Fill burrows as recommended
above. Constant vigilance and
removal of cuttings placed in
spillways is also necessary.
- 35 -
c.
Earthwork. As outlined in Section 2.0, there are many different causes of deterioration of the
earth surfaces of a dam. For example, wave action may cause erosion (scarps) along the upstream
slope, vehicles may cause ruts in the crest, or runoff waters may leave erosion gullies on the upstream
and downstream slopes and in earthen spillways. Damage of this nature must be repaired on a continual
basis.
Minor soil erosion is easily repaired. The first consideration is to use new soil material similar in makeup
to the soil lost. The new soil should not contain vegetation, organic matter, trash or large rock fragments.
In addition, the new soil should be neither too wet nor too dry, but should contain enough moisture to
enable good compaction. Prior to placing new soil, the repair area must be prepared by removing all
loose and/or unsuitable material such as loose soil, brush, roots, trash, or large rocks. Finally, the new
soil should be placed in thin layers, six inches or less, and hand tamped until firm.
In order to prevent future erosion, consideration should be given to protecting the repaired area with
erosion resistant rock or other material (i.e. concrete or asphalt) if appropriate.
d.
Concrete. Even though concrete is an extremely durable material, periodic maintenance is
required to repair deteriorated areas. Deteriorated areas are usually in the form of weathering or cracking
as discussed in Section 2.0.
In general, it is a good practice to repair concrete deterioration in the early stages when it is most
manageable. However, concrete deterioration can be either active or relatively stable. Active deterioration
is caused by factors and elements that are on-going and have yet to stabilize. These factors are likely to
result in additional deterioration and even damage to any repairs. Relatively stable deterioration is caused
by factors and elements that are not expected to occur again. Concrete deterioration can be generated by
so many varying conditions, it is often impossible to list them all, but often the reason is apparent to an
experienced engineer. Such consultation should be sought prior to attempting any concrete repairs.
For additional information regarding general concrete repair, see References 3, 5, 6 and 35 identified in
Appendix C.
e.
Conduits. The conduits (or pipes) through a dam are some of its most important features
and must be adequately maintained. The outlet conduit not only includes the pipe transporting the water
but also the trash rack at the inlet to prevent debris from entering and clogging the pipe.
1.
Internal Maintenance. Problems detected during inspection of the conduits should be
immediately addressed and subsequently checked to make sure that the repair was effective. Due to the
importance of the conduit and the difficulty of properly repairing it, professional supervision should be
obtained.
2.
Trash Racks. Maintenance should include periodically checking the rack for rusted and
broken sections and repairing as needed. The trash rack should be checked frequently during and after
storm events to ensure it is functioning properly and to remove accumulated debris.
f.
Mechanical. It is essential that stored water be released when required. An operable outlet
provides the only means for emergency drawdown of the reservoir and is essential to the dam's safety.
Table 3.1 lists the required mechanical maintenance procedures, their purpose, recommended time
intervals, and comments.
- 36 -
g.
Electrical. In general, electricity is used on dams for the following:

provide lighting

operate outlet gates

operate recording equipment

operate spillway gates

operate other electrical equipment like elevators or cranes
Thus, it is important that the electrical system be well maintained.
Maintenance should include a thorough check of the fuses and a test of the system to be sure everything
is properly functioning. Moisture and dust should be kept away from the electrical system, and wiring
should be checked for corrosion and mineral deposits. Any necessary repairs should be completed
immediately, and records of the repair work should be kept.
In addition, generators kept for back-up emergency power must be maintained. Maintenance should
include oil changes, battery checks, antifreeze checks and making sure that fuel is readily available.
h.
Hydraulic. A hydraulic control system is often used to open and close the valves or sliding
gates of the outlet or intake works. The hydraulic system usually has long hoses and pipelines to transmit
hydraulic fluid to the gate-operating cylinders, and there are gauges to indicate hydraulic pressure in the
system. Routine checks should be performed on the hydraulic cylinders, hoses and pipelines as required.
Table 3.1
MECHANICAL MAINTENANCE PROCEDURES
Maintenance
Procedure
Recommended Time
Interval
Purpose
1. Cycle outlet gates
through full operating
range*
Prevents buildup of rust on
contact surfaces of the
operating mechanism and
possible
seizure
of
mechanism due to operating
parts rusting together
Semi-annually
(unless
otherwise directed by gate
manufacturer)
2. Lubrication
To reduce wear and protect
mechanism against adverse
effects of weather
Per manufacturer’s instructions or as needed.
3. Painting or greasing of
ferrous metal
Prevent erosion
Annually or as needed
- 37 -
Comments
Notes should be made of
operating characteristics.
Rough, noisy, or erratic
movement of the gate
should be noted and investigated immediately.
When repainting areas, do
not allow paint to get on
gate seats, gate wedges,
Maintenance
Procedure
Recommended Time
Interval
Purpose
Comments
gate stems in the reach
where the stems pass
through the stem guides,
or other friction surfaces
where paint could cause
binding. Heavy grease
should be applied on surfaces where binding can
occur.
4. Aligning and tightening
of stem guides or
brackets
5. Readjustment of wedge
system
Decrease leakage
As needed as noted by
inspection
Adjustment should never
be attempted by inexperienced
personnel.
Always employ experienced personnel recommended by gate supplier
or manufacturer.
*It is recommended that cycling be done during periods of low reservoir storage to prevent large outlet
discharges.
i.
Miscellaneous.
1.
Access Roads. For a dam to be operated and maintained there must be a safe means
of access to it at all times. The road surface must be maintained to allow safe passage of automobiles
and any required equipment for servicing the dam, in any weather conditions. Routine observations of
any cut and fill slopes along the sides of the road should be made. If unstable conditions develop,
professional help should be obtained and remedial measures initiated.
2.
Monitoring Devices. Monitoring devices, as presented in Section 1.4, for the most part
do not require routine maintenance. The main exceptions are the piezometers, weirs and stakes (in
staked areas). The weirs should be regularly checked and cleared of any debris. They should also be
checked for loose boards or loose metal stripping, and repaired as necessary.
Staked areas are particularly susceptible to vandalism. Stakes should be checked routinely and replaced
immediately where needed.
Piezometers are to be maintained in an operable state at all times. Consult the recommendations of the
manufacturer for guidelines on maintenance.
- 38 -
3.
Winterizing. Ice can exert excessive force and damage various components of a dam.
In addition, ice formation in and around spillways, and in conduit outlets, can cause blockages and
prevent their proper functioning. Ice formation can be prevented by heaters, aeration equipment, or forced
movement of water. The owner/operator should be aware of these potential problems and take
appropriate action during severe cold spells.
4.
Vandalism Prevention. Vandalism is a common problem whose best solution is
prevention. Initial costs of installation of fences to prevent access to the area of the dam by unauthorized
persons, and providing heavy duty doors and locks on buildings housing equipment, are realized many
times over. As many measures as possible should be undertaken to prevent vandalism and protect all
equipment and surfaces from the public. Also, owners should be aware of their responsibility for public
safety, including the safety of people not authorized to use the facility. "No Trespassing" signs should be
posted, and fences and warning signs should be erected around dangerous areas. It is recommended
that the dam owner regularly consult with an insurance professional to assess the adequacy of existing
liability insurance.
3.4
Maintenance Schedule
Every dam owner should develop a schedule of regular routine maintenance and incorporate it as part of
the overall operation plan for the facility. In general, it is recommended that the entire program of
maintenance be performed at least twice per year. Preferably, maintenance should be performed once in
the spring, soon after winter snowmelt, and once in the late fall, sometime before the first snowfall. In
addition, each dam owner should assess whether his facility has areas or items which require
maintenance on a more frequent basis (i.e., daily, weekly, or monthly).
3.5
Maintenance Records
As in the case of inspection records, thorough maintenance records are of utmost importance. A record
should be kept of all maintenance activities. Information to be recorded should include the following as a
minimum:

Date and time of maintenance.

Testing and exercising of outlet and spillway gates and valves, controls, and standby
equipment

Maintenance activities such as lubrication, cleaning, clearing debris from channels, tree
removal, repairing erosion, etc.
The data should be recorded by the person responsible for maintenance.
- 39 -
- 40 -
SECTION 4.0
DAM OPERATION
- 41 -
SECTION 4.0 - DAM OPERATION
4.1
General
a.
Introduction. The purpose of developing and implementing operating procedures or an
operation plan is to provide for maximum dam safety by formalizing a regular schedule of routine tasks.
An effective operations plan provides the information and instruction needed to allow an inexperienced
person to perform all the tasks required to operate and maintain a dam safely.
Assembling the required information and writing a custom-made operation plan is the responsibility of the
dam owner/operator. This section is intended to serve as a guide to assist the dam owner/operator in
preparing such a plan. Additional assistance from an experienced consulting engineer may also be
helpful.
b.
Elements of an Operation Plan. The extent of an operation plan is dependent on the
complexity of the dam itself. Contributing factors include dam size, number of appurtenances, and, in
particular, the number of operable mechanisms. Nevertheless, the most effective plans are usually the
simplest.
The principal elements of an effective operation plan are briefly presented below.
Section I: Background Data — A typical dam owner/operator possess a good deal of information about
his facility. Very often the information is scattered about or reviewed so rarely as to make it of
little use. This section of the operation plan serves to organize available background data to
make it more accessible.
Section I
Schedule of Routine Tasks — A schedule that includes both day-to-day tasks and tasks
performed less frequently through a given year. The schedule serves to formalize inspection
and maintenance procedures such that an inexperienced person could determine when a task
is to be performed by merely consulting the schedule.
Section Ill: Emergency Procedures — This is perhaps the most important section. It contains a formal
plan for reacting to dam emergencies. It involves coordination between the dam
owner/operator, local agencies and downstream residents.
4.2
Operation Plan
a.
Section I — Background Data. Prior to assembling the items suggested below, the dam
owner/operator will need to gather all the information in his possession regarding the dam. Examples may
include design reports, photographs, plans, maps and miscellaneous correspondence pertaining to the
facility.
1.
Vital Dam Statistics. Compile a list of dam statistics including the following (For
definitions of terms refer to Appendix D of this manual).
a)
Embankment
-
b)
Type of Dam
Height of Dam
Length of Crest
Width of Crest
Angle of Upstream Slope
Angle of Downstream Slope
Available Freeboard
Spillway
- Type of Spillway
- Length of Spillway Crest
- Spillway Crest Elevation
- Normal Pool Elevation
- 42 -
-
Top of Dam Elevation
DEP I. D. Number
County Location
Township Location
Stream Name
Year Completed
Hazard Classification
-
Available Freeboard
Greatest depth of flow ever observed over
spillway crest including date of occurrence
c)
Outlet Statistics
- Size and Type of Outlet
- Size and Type of Outlet Control Device - Inlet
Invert Elevation
- Outlet Invert Elevation
2.
Description of Appurtenances. As briefly as possible, describe the various
appurtenances of the facility, including location and function. Include sketches and photographs as often
as possible. Any operable or self-regulating appurtenance should be included. Typically the list will
contain the following:
-
Spillway
Spillway Gates
Outlet Conduit Control device
Monitoring Devices
3.
Operating Instructions for Operable Mechanisms. Develop a clear, step-by-step set
of instructions for operating all operable mechanisms associated with the dam. This will typically include
the outlet conduit control valve or possibly the spillway gates if applicable. The instructions should be
complete regardless of the relative degree of simplicity or complexity involved. Emphasize proper
sequence and include sketches, drawings and photographs to aid in identifying specific handles, cranks,
buttons, etc.
4.
Monitoring Instructions and Forms. Instructions on how to utilize monitoring
instruments and how to take measurements at monitoring points must be provided. A map identifying
each instrument and monitoring point should be included. Forms for recording the data will also be
needed. The assistance of a qualified engineer may be useful in developing this section.
5.
Maintenance Instructions. Any special instructions for performing periodic
maintenance should be given in detail. This will allow new personnel to understand the task and
experienced personnel to make sure that they have completed the work properly (consult Section 3).
6.
Information Bibliography. Catalog all available background data in a single listing.
Include titles, authors or agencies responsible for publication, date or origin, brief description and
permanent location of material (e.g., filing cabinet in basement). Even materials without titles or authors
such as photographs and maintenance information should be listed.
7.
Telephone List A comprehensive up-to-date listing of important telephone numbers
should include the following (see Appendix A). •
-
Owner/operator (home and office)
Employees actively involved with dam.
Local emergency management (civil defense) agencies (county and municipal).
State Police
Local police and fire departments.
Qualified local engineering consultants.
DEP's Division of Dam Safety
Downstream residents (if practical).
b.
Section II – Schedule of Routine Tasks. The four categories of routine tasks are as follows:
operating tasks, maintenance tasks, inspection tasks and monitoring tasks. The frequency of required
performance of a given task is dependent upon factors peculiar to the dam itself such as hazard
classification (see Reference 22 Appendix C). Suggested minimum frequencies for various activities are:
1.
Category 1 ―High Hazard‖ Dams. Failure of the dam would cause excessive
economic loss and would result in substantial loss of human life.
Daily – Surveillance by the dam owner/operator or caretaker.
Weekly – Monitoring of seepage.
- 43 -
Monthly – Gathering, immediately plotting and interpreting observation well and piezometer data.
Quarterly – Visual inspection by dam owner/operator.
Bi-Annually – Test operation of outlet and spillway mechanical components.
Annually – Inspection by a qualified registered professional engineer. Reading horizontal and
vertical control monuments (more frequently if necessary).
Routine maintenance as required.
Additional Inspections – Immediately following excessive flooding and/or earthquake shaking.
2.
Category 2 ‖High Hazard‖ Dams. Failure of the dam would cause appreciable
economic loss and could result in the loss of a few human lives.
Weekly – Surveillance by the dam owner/operator or caretaker.
Monthly – Gathering, plotting and interpreting observation well and piezometer data.
Quarterly – Visual inspection by dam owner/operator.
Annually – Inspection by a qualified registered professing engineer. Test operation of outlet
and spillway mechanical components. Reading horizontal and vertical control
monuments (more frequently if necessary).
Routine maintenance as required
Additional Inspections – Immediately following excessive flooding and/or earthquake shaking.
3.
All ―Non-High Hazard‖ Category 3 and Category 4 Dams. Failure would cause
minimal economic damage and no loss of life would be expected.
Monthly – Surveillance by the dam owner/operator or caretaker. Monitoring of seepage. Gathering,
plotting and interpreting observation well and piezometer data.
Annually – Visual inspection by dam owner/operator. Testing of the outlet.
Every Five Years – Reading of horizontal and vertical control monuments.
Route maintenance as required.
Additional Inspections – Immediately following excessive flooding and/or earthquake shaking.
c.
Section Ill – Emergency Action Plan. Pennsylvania law requires the dam owner/operator of
any dam or reservoir that may cause loss of life or substantial property damage as a result of failure to
develop an Emergency Action Plan.
An Emergency Action Plan (EAP) is a formal document that identifies potential emergency conditions at a
dam and specifies preplanned actions to be followed in response to a dam hazard emergency, which are
designed to minimize property damage and prevent loss of life.
The EAP describes procedures and information to assist the dam owner in surveillance of developing
conditions and issuing timely notification of an emergency situation to responsible emergency
management authorities. It also contains inundation maps that show the emergency management
authorities the critical areas for action in the event of a dam hazard emergency.
An EAP must be tailored to a dam’s specific conditions, to the capabilities of the owner and operator, and
to the emergency response organizations that will implement the EAP. Your county’s emergency
management office, the Pennsylvania Emergency Management Agency (PEMA), and DEP’s Division of
Dam Safety all have a hand in review and approval of a dam emergency action plan.
If your dam requires an Emergency Action Plan and you do not have one approved, or if your EAP was
approved more than four years ago, you should develop or revise your EAP according to the DEP /
PEMA publication: GUIDELINES FOR DEVELOPING AN EMERGENCY ACTION PLAN (EAP) FOR
HAZARD POTENTIAL CATEGORY 1 and 2 DAMS. (DEP Publication No. 3140-BK-DEP1956). The EAP
guidelines booklet is available from DEP’s Division of Dam Safety, along with a data CD including a
sample plan template and other publications. The guidelines and other documents can be viewed and
downloaded via DEP’s public eLibrary. (From the DEP website at: www.dep.state.pa.us select Forms &
- 44 -
Publications under the Quick Access menu at the left of the home page. Then look under
Publications, then Waterways Engineering, then Dam Safety for all available publications).
The Emergency Action Plan must be followed in the event of a dam hazard emergency. A dam hazard
emergency refers to any condition that the dam owner/operator or the DEP finds to be an imminent threat
to life or property above or below a dam — whether arising from the condition of the dam or extraordinary
natural conditions — including, but not limited to, flood, earthquake, fire and ice jam.
In general, an effective EAP establishes and/or identifies the following:

The areas that will be flooded and to what severity.

Whom to notify for evacuation in case of an emergency, and when.

Where evacuees will be housed or sheltered in the event of extensive damage to
residential structures.

The routes and roadways to be used as evacuation routes. Where roadblocks
will be needed along potentially flooded routes. The agencies and/or persons
who will be required to perform which tasks.

A primary and backup communication system that considers the possibility of a
power blackout.
A predetermined time should be established when evacuation efforts are to be terminated. Previous
studies may be available to indicate what flood level is no longer safe to continue evacuation in each
area. Upstream flood levels, crest travel time, and time needed to evacuate all people and equipment
should be the determining factors in terminating evacuation assistance.
The farther downstream a damage center is located, the more chance there is for a long flood warning
and more time to carry out an organized evacuation. Protection of life should also be considered before
anything else in an evacuation effort.
The Act of May 16, 1985 (Act 1985-15), amended Section 13 of the Dam Safety and Encroachments Act
(35 P.S. 093.13) to add the following new subsection (b):
"(b) In addition to the duties of subsection (a), the owner of any high hazard dam which has been
classified as such by the DEP shall post notices in public places in any area which might be affected by
the failure of the dam'
The Act defines "high hazard dam” as "any dam so located as to endanger populated areas downstream
by its failure.” This definition includes any dams categorized as Hazard Classifications 1 and 2 under the
Department's Chapter 105. Upon review, some Category 2 dams may be exempted from this
requirement.
The permittee or owner of a hazard potential Category 1 or Category 2 dam must post notices in public
locations in areas that may be affected by the failure of the dam. Also, the notice must be posted by the
permittee or owner in public places within each political subdivision situated within the inundation area
downstream of the dam. The notice must be posted in the city, borough and township buildings in the
affected municipalities, with the management’s permission. Additionally, the notice shall be posted in
locations within the inundation area, such as, post offices, libraries, grocery stores or gas stations, with
the management’s permission.
The Notice shall state that a copy of the Emergency Action Plan for the dam is available for inspection at
the following locations:
(1)
County Emergency Management Offices (list locations)
(2)
Municipal Emergency Management Offices (list locations)
(3)
Offices or Residence of the Dam Owner (list location)
- 45 -
NOTICE
DAM HAS BEEN CLASSIFIED BY THE
DEPARTMENT OF ENVIRONMENTAL PROTECTION, DIVISION OF
DAM SAFETY, AS A HIGH HAZARD DAM; THIS IS A DAM SO
LOCATED AS TO ENDANGER POPULATED AREAS DOWNSTREAM BY
ITS FAILURE.
AN EMERGENCY ACTION PLAN HAS BEEN DEVELOPED FOR
(NAME OF DAM)
A COPY OF THIS PLAN, INCLUDING AN INUNDATION MAP NOTING
AREAS IN
(NAME OF MUNICIPALITY AND/OR MUNICIPALITIES))
SUBJECT TO FLOODING IN THE EVENT OF FAILURE, IS AVAILABLE
FOR PUBLIC INSPECTION AT THE FOLLOWING LOCATIONS:
(DAM OWNER & ADDRESS)
(LOCAL EMA OFFICE & ADDRESS)
(COUNTY EMA OFFICE & ADDRESS)
(LOCAL EMA OFFICE & ADDRESS)
This NOTICE is posted per Department of Environmental Protection’s
Chapter 105 Dam Safety and Waterway Management §105.134(c).
- 46 -
APPENDIX A
IMPORTANT TELEPHONE NUMBERS AND ADDRESSES
- 47 -
For more information about dams in Pennsylvania and DEP’s Dam Safety Program, contact:
Department of Environmental Protection
Bureau of Waterways Engineering and Wetlands
Division of Dam Safety
P.O. Box 8554
Harrisburg, PA 17105-8554
717-787-8568
DEP’s Watershed Management Program
Regional Offices
Northwest Region
230 Chestnut St.
Meadville, PA 16335-3481
814-332-6984
Northcentral Region
208 W. Third St., Suite 101
Williamsport, PA 17701
570-327-3574
Northeast Region
2 Public Square
Wilkes-Barre, PA 18711-0790
570-830-3093
Counties: Butler, Clarion, Crawford,
Elk, Erie, Forest, Jefferson, Lawrence,
McKean, Mercer, Venango and Warren
Counties: Bradford, Cameron,
Clearfield, Centre, Clinton, Columbia,
Lycoming, Montour, Northumberland,
Potter, Snyder, Sullivan, Tioga and
Union
Counties: Carbon, Lackawanna,
Lehigh, Luzerne, Monroe, Northampton,
Pike, Schuylkill, Susquehanna, Wayne
and Wyoming
Southwest Region
400 Waterfront Drive
Pittsburgh, PA 15222-4745
412-442-4000
Southcentral Region
909 Elmerton Ave.
Harrisburg, PA 17110
717-705-4707
Southeast Region
2 East Main St.
Norristown, PA 19401
484-250-5970
Counties: Allegheny, Armstrong,
Beaver, Cambria, Fayette, Greene,
Indiana, Somerset, Washington and
Westmoreland
Counties: Adams, Bedford, Berks,
Blair, Cumberland, Dauphin, Franklin,
Fulton, Huntingdon, Juniata, Lancaster,
Lebanon, Mifflin, Perry and York
Counties: Bucks, Chester, Delaware,
Montgomery and Philadelphia
For more information, visit www.dep.state.pa.us, keyword: Dam Safety.
- 48 -
PENNSYLVANIA EMERGENCY MANAGEMENT AREA OFFICES
Western Area Office
Pennsylvania Emergency Management Agency
276 Stormer Road
Indiana, PA 15701-8933
Emergency Tel: 717-651-2001
Non-Emergency Tel: 724-357-2990
Central Area Office
Pennsylvania Emergency Management Agency
2605 Interstate Drive
Harrisburg, PA 17110-9364
Emergency Tel: 717-651-2001
Non-Emergency Tel: 717-651-7060
Eastern Area Office
Pennsylvania Emergency Management Agency
Hamburg Center
Hamburg, PA 19526
Emergency Tel: 717-651-2001
Non-Emergency Tel: 610-562-3003
PEMA - State Emergency Operations Center
2605 Interstate Drive
Harrisburg, PA 17110-9364
Tel: 717-651-2001
800-424-7362
- 49 -
APPENDIX B
INSPECTION CHECKLISTS
This and other forms and publications can be viewed, printed and
saved to your own computer from the Dam Safety homepage at
www.depweb.state.pa.us/waterwayseng, then click on Dam Safety.
- 50 -
- 51 -
DAM INSPECTION CHECKLIST
Pennsylvania Department of Environmental Protection
Bureau of Waterways Engineering
Division of Dam Safety
NAME OF DAM:
LOCATION:
DEP DAM NO.: D
Municipality:
-
County:
DEP CLASSIFICATION DATA:
Size:
Hazard:
PHYSICAL DATA:
Type of Dam:
Height of Dam:
ELEVATIONS:
Normal Pool:
Pool at Inspection:
Normal Pool Storage Capacity:
DAM OWNER:
Tailwater at Inspection:
OPERATOR:
ADDRESS:
PHONE: (
)FAX NO.: (
)E-MAIL ADDRESS:
A completed and signed Dam Owners Notice Checklist is to accompany this Inspection Checklist.
PERSONS PRESENT AT INSPECTION:
Name
Title/Position
Representing
DATE OF INSPECTION:
/
/
WEATHER:
TEMPERATURE:
This is to certify that the above dam has been inspected and
the following are the results of this inspection.
Signature of Registered Professional Engineer
(P.E. Seal Required)
Date Revised: 1/2009
- 52 -
Date
COMMENTS
REPAIR
DATE:
IVESTIGATE
CONDITION
DEP DAM NO.:
MONITOR
ITEM
NAME OF DAM:
EMBANKMENT: CREST
1
2
3
4
5
6
7
8
9
Surface Cracking
Sinkhole, Animal Burrow
Low Area(s)
Horizontal Alignment
Ruts and/or Puddles
Vegetation Condition
Warning Signs
Additional Comments (Refer to item number if applicable):
EMBANKMENT: UPSTREAM FACE
10
11
12
13
14
15
16
17
Slide, Slough, Scarp
Slope Protection
Sinkhole, Animal Burrow
Emb.-Abut. Contact
Erosion
Vegetation Condition
Additional Comments (Refer to item number if applicable):
Dam Safety High Hazard Dam Inspection Checklist
Page 2 of 10
Date Revised: 1/09-
COMMENTS
REPAIR
CONDITION
DATE:
IVESTIGATE
DEP DAM NO.:
MONITOR
ITEM
NAME OF DAM:
EMBANKMENT: DOWNSTREAM FACE
18
19
20
21
22
23
24
25
26
27
Wet Area(s) (No Flow)
Seepage
Slide, Slough, Scarp
Emb. - Abut. Contact
Sinkhole, Animal Burrow
Erosion
Unusual Movement
Vegetation Control
Additional Comments (Refer to item number if applicable):
EMBANKMENT: INSTRUMENTATION
28
29
30
31
32
33
34
35
36
37
Piezometers/Observ.
Wells
Staff Gauge and Recorder
Weirs
Survey Monuments
Drains
Low Flow Release
Frequency of Readings
Location of Records
Additional Comments (Refer to item number if applicable):
Dam Safety High Hazard Dam Inspection Checklist
Page 3 of 10
Date Revised: 1/09-
COMMENTS
REPAIR
DATE:
IVESTIGATE
CONDITION
DEP DAM NO.:
MONITOR
ITEM
NAME OF DAM:
DOWNSTREAM AREA
38
39
40
41
42
43
44
45
46
47
Abutment Leakage
Foundation Seepage
Slide, Slough, Scarp
Drainage System
Boils
Wet Areas
Reservoir Slopes
Access Roads
Security Devices
Act 91 Run-of-the-River
Signs or Bouys
48
49
Additional Comments (Refer to item number if applicable):
SPILLWAYS: ERODABLE CHANNEL
50
51
52
53
54
55
Slide, Slough, Scarp
Erosion
Vegetation Condition
Debris
Additional Comments (Refer to item number if applicable):
Dam Safety High Hazard Dam Inspection Checklist
Page 4 of 10
Date Revised: 1/09-
COMMENTS
REPAIR
DATE:
IVESTIGATE
CONDITION
DEP DAM NO.:
MONITOR
ITEM
NAME OF DAM:
SPILLWAYS: NON-ERODABLE CHANNEL
56
57
58
59
60
61
62
63
64
Sidewalls
Channel Floor
Unusual Movement
Approach Area
Weir or Control
Discharge Channel
Boils
Additional Comments (Refer to item number if applicable):
SPILLWAYS: DROP INLET
65
66
67
68
69
Intake Structure
Trashrack
Stilling Basin
Additional Comments (Refer to item number if applicable):
Dam Safety High Hazard Dam Inspection Checklist
Page 5 of 10
Date Revised: 1/09-
COMMENTS
REPAIR
CONDITION
DATE:
IVESTIGATE
DEP DAM NO.:
MONITOR
ITEM
NAME OF DAM:
OUTLET WORKS
70
71
72
73
74
75
76
77
78
79
80
81
82
Intake Structure
Trashrack
Stilling Basin
Primary Closure
Secondary Closure
Control Mechanism
Outlet Pipe
Outlet Tower
Outlet Structure
Seepage
Unusual Movement
Additional Comments (Refer to item number if applicable):
CONCRETE/MASONRY DAMS: UPSTREAM FACE
83
84
85
86
87
88
Surface Conditions
Condition of Joints
Unusual Movement
Abutment-Dam Contacts
Additional Comments (Refer to item number if applicable):
Dam Safety High Hazard Dam Inspection Checklist
Page 6 of 10
Date Revised: 1/09-
COMMENTS
REPAIR
CONDITION
DATE:
IVESTIGATE
DEP DAM NO.:
MONITOR
ITEM
NAME OF DAM:
CONCRETE/MASONRY DAMS: DOWNSTREAM FACE
89
90
91
92
93
94
95
96
Surface Conditions
Condition of Joints
Unusual Movement
Abutment-Dam Contacts
Drains
Leakage
Additional Comments (Refer to item number if applicable):
CONCRETE/MASONRY DAMS: CREST
97
98
99
100
101
102
103
Surface Conditions
Horizontal Alignment
Vertical Alignment
Condition of Joints
Unusual Movements
Additional Comments (Refer to item number if applicable):
Dam Safety High Hazard Dam Inspection Checklist
Page 7 of 10
Date Revised: 1/09-
COMMENTS
REPAIR
DATE:
IVESTIGATE
CONDITION
DEP DAM NO.:
MONITOR
ITEM
NAME OF DAM:
RESERVOIR AREA
104
105
106
107
108
109
110
111
Sedimentation
Slope Stability
Sinkholes
Fractures
Unwanted Growth
Storage Gage
Additional Comments (Refer to item number if applicable):
Final Comments:
Dam Safety High Hazard Dam Inspection Checklist
Page 8 of 10
Date Revised: 1/09-
DAM OWNERS NOTICE CHECKLIST
Pennsylvania Department of Environmental Protection
Bureau of Waterways Engineering
Division of Dam Safety
NAME OF DAM:
DEP DAM NO.:
This is to certify that both the Downstream Hazard Description is accurate and the Posted Notice
locations listed below have been inspected and the following are the results of these inspections.
Name of Dam Owner
Signature of Dam Owner
Date
This Dam Owners Notice Checklist is to accompany the Inspection Checklist filed by the Engineer.
EMERGENCY ACTION PLAN
Date of Last Update of Emergency Plan:
Downstream Hazard Description (Refer to sections II.C and II.D in the EAP), additionally, specify any new
developments, structures, etc. downstream within the inundation area:
COMMENTS
REPLACED
LOCATION
MISSIING
DATE
INSPECTED
(Refer to section V.A in the EAP)
EXISTING
ITEM
POSTED NOTICES
1
2
3
4
5
6
7
8
9
10
11
12
Additional Comments (Refer to item number if applicable):
Dam Safety High Hazard Dam Inspection Checklist
Page 9 of 10
Date Revised: 1/09-
Dam Safety High Hazard Dam Inspection Checklist
Page 10 of 10
Date Revised: 1/09-
APPENDIX C
REFERENCE LIST
(Original Edition)
- 61 -
REFERENCES
1.
ASCE/USCOLD (1975) Lessons from Dam Incidents, USA, American Society of Civil Engineers,
New York.
2.
American Concrete Institute (1968) "Guide for Making a Condition Survey of Concrete in Service,"
Journal of the American Concrete Institute, Proceedings, Vol. 65, No. 11, pp. 905-918.
3.
American Concrete Institute (1982) ACE Manual of Concrete Practice 1982, Part 7, Materials and
General Properties of Concrete, American Concrete Institute, Detroit, Michigan.
4.
Chief of Engineers (1975) Recommended Guidelines for Safety Inspection of Dams, National
Program of Inspection of Dams, Vol. I, Appendix ID, Dept. of the Army, Washington, D.C.
5.
Concrete Construction Publication, Inc. (1983) Four Steps to Successful Concrete Repair, Volume
28. Number 1, Addison, Illinois, January.
6.
Concrete Construction Publication, Inc. (1985) Crack Repair, Volume 30, Number 1, Addision,
Illinois, January.
7.
Federal Coordinating Council for Science, Engineering and Technology, Ad Hoc Interagency
Committee on Dam Safety (1979) Federal Guidelines for Dam Safety, Federal Emergency
Management Agency, Government Printing Office, Washington, D.C.
8.
Federal Emergency Management Agency (1982) Interagency Committee on Dam Safety (ICODS),
Subcommittee on Emergency Action Planning, Dam Safety, Emergency Action Planning.
9.
Forest Service And Soil Conservation Service, U.S. Dept of Agriculture (1980) Guide for Safety
Evaluation and Periodic Inspection of Existing Dams.
10.
Golze, A.R., ed. (1977) Handbook of Dam Engineering, Van Nostrand Reinhold Co., New York.
11.
Honaker, Harry Keith, Guidelines for Maintenance and inspection of Dams in Kentucky, Kentucky
Division of Water Resources.
12.
ICOLD (1969) General Considerations Applicable to Instrumentation for Earth and Rock fill Dams,
Committee on Observations of Dams and Models, Bulletin No. 21, November.
13.
!COLD (1981) Automated Observation for Instantaneous Safety Control of Dams and Reservoirs,
Bulletin No. 41, January.
14.
Jansen, R. B. (1968) A Prescription for Dam Safety— Instrumentation and Surveillance,
Conference of College of Engineering, University of California, Berkeley.
15.
Jansen, R. B. (1980) Dams and Public Safety, U.S. Bureau of Reclamation, Government Printing
Office, Washington, D.C. (reprinted in 1983).
16.
Mills, George E.'(1983) Operation, Maintenance, and Inspection Manual for Dams, Dikes, and
Levees, Ohio Department of Natural Resources.
17.
Mine Safety and Health Administration, Mine Waste and Geotechnical Engineering Division (1984)
Construction Inspection of Dams and Coal Refuse Embankments, Bruceton Mills, Pennsylvania.
18.
National Association of Conservation Districts "Darn Safety — Who is Responsible?", slide show
produced by National Association of Conservation Districts, Washington, D.C.
19.
National Research Council (1982) Geotechnical Instrumentation for Monitoring Field Performance,
National Academy Press, Washington, D.C.
20.
National Research Council, Committee on the Safety of Existing Dams (1983) Safety Evaluation of
Existing Dams, Evaluation and Improvement, National Academy Press, Washington, D.C.
21.
Pennsylvania State Legislature (1978) Pennsylvania Dam Safety Encroachments Act as amended
(32 P.S. §§693.1-693.27).
- 62 -
22.
Pennsylvania Environmental Quality Board (1980) Chapter 105. Dam Safety and Waterway
Management, Rules and Regulations.
23.
Schurer, John, et. al. (1983) State of Colorado Dam Safety Manual, State Engineer's Office,
Colorado.
24.
Sharma and Raphael (1979/1981) Genera! Considerations on Reservoir Instrumentation,
Committee on Measurements, USCOLD.
25.
Sowers, C. F. (1961) "The Use and Misuse of Earth Dams:' Consulting Engineering, July.
26.
Spear, Andrew D. (1981) PP&L Owned Dams and Related Facilities Inspection Program,
Pennsylvania Power and Light Company, Allentown, Pennsylvania.
27.
State of Illinois, Department of Water Resources (1980) Guidelines and Forms for Inspection of
Illinois Dams, Springfield, Illinois.
28.
Tschantz, Bruce A. (1972) The Inspection and Maintenance of Privately Owned Dams in
Tennessee, University of Tennessee.
29.
USCOLD (1983) Guidelines for inspection of Dams Following Earthquakes, U.S. Government
Printing Office.
30.
U.S. Army Corps of Engineers (1971 and 1976) Instrumentation of Earth and Rock fill Dams, Parts
1 and 2, EM 1110-2-1908, August 1971 and November 1976.
31.
U.S. Army Corps of Engineers (1980a) Flood Emergency Plans, Guidelines for Corps Dams,
Hydrologic Engineering Center, Davis, California, June, 47 pp.
32.
U.S. Army Corps of Engineers (1980b) Instrumentation for Measurement of Structural Behavior of
Concrete Structures, EM 1110-2-4300, September.
33.
U.S. Army Corps of Engineers (1982b)National Program for Inspection of Non-Federal Dams—
Final Report to Congress.
34.
U.S. Dept. of the Interior, Bureau of Reclamation (1974) Earth Manual, 2d. ed., Government
Printing Office, Washington, D.C.
35.
U.S. Department of the Interior, Bureau of Reclamation (1975) Concrete Manual, A Water
Resources Technical Publication, U.S. Bureau of Reclamation, Government Printing Office,
Washington, D.C.
36.
U.S. Dept. of the Interior, Bureau of Reclamation (1977) Design of Arch Dams, Denver, Colorado.
37.
U.S. Dept. of the Interior, Bureau of Reclamation (1977) Design of Arch Dams, Denver, Colorado.
38.
U.S. Dept. of the Interior, Bureau of Reclamation (1977) Design of Small Dams, Denver Colorado.
39.
U.S. Dept of the Interior, Bureau of Reclamation, Division of Dam and Structural Safety (1982)
Operation and Maintenance Guidelines for Small Dams.
40.
U.S. Dept of the Interior, Bureau of Reclamation (1983) Safety Evaluation of Existing Dams, A
Water Resources Technical Publication, Denver, Colorado.
41.
Virginia State Water Control Board, Bureau of Water Control Management (1983) Safety Evaluation
of Small Earth Dams, Information Bulletin 549, Richmond, Virginia.
42.
Wilson, S. D., and Handcock, C. W, Jr. (1965) "Instrumentation for Movements Within Rockfill
Dams," Instruments and Apparatus for Soil and Rock Mechanics, ASTM STP 392, American
Society of Testing Materials, pp. 115-130.
43.
Wilson, S. D. (1973)"Deformation of Earth and Rockfill Dams," Embankment-Dam Engineering,
Casagrande Volume, John Wiley &Sons, New York.
- 63 -
APPENDIX D
GLOSSARY OF TERMS
- 64 -
APPENDIX D
GLOSSARY OF TERMS
ABUTMENT – That part of the valley side against which the dam is constructed. An artificial abutment is
sometimes constructed, as a concrete gravity section, to take the thrust of an arch dam where
there is no suitable natural abutment. Right and left abutments are those on respective sides of
an observer when viewed looking downstream
ACT The Dam Safety and Encroachments Act (32 P.S. §§693.1-693.27).
AMBERSON DAM – See Buttress Dam.
APPURTENANT STRUCTURES – Refers to ancillary features of a dam, such as the outlet, spillway,
outlet conduit, tunnels, etc.
ARCH DAM – A concrete or masonry dam that is curved in plan so as to transmit the major part of the
water load to the abutments.
AS-BUILT DRAWINGS – Plans or drawings portraying the actual dimensions and conditions of a dam,
dike or levee as it was built. Field conditions and material availability during construction often
require changes from the original design drawings.
AUXILIARY SPILLWAY – See Spillway.
AXIS OF DAM – The plane or curved surface, arbitrarily chosen by a designer, appearing as a line, in
plan or in cross section, to which the horizontal dimensions of the dam can be referred.
BASE WIDTH (BASE THICKNESS) – The maximum thickness or width between upstream and
downstream faces and normal to the axis of the dam but excluding projections for outlets, etc.
BEACHING – The removal by wave action of a portion of the upstream (reservoir) side of the
embankment and the resultant deposition of this material farther down the slope. Such deposition
creates a relatively flat beach area.
BERM – A horizontal step or bench in the sloping profile of an embankment dam. BLANKET
DRAINAGE BLANKET – A drainage layer placed directly over the foundation material.
UPSTREAM BLANKET – An impervious layer placed on the reservoir floor upstream of a dam. In the
case of an embankment dam the blanket may be connected to the impermeable element in the
dam.
BOIL – A disturbance in the surface layer of soil caused by water escaping under pressure from behind a
water retaining structure such as a dam or a levee. The boil may be accompanied by deposition
of soil particles (usually sand) in the form of a ring (miniature volcano) around the area where the
water escapes.
BREACH – An opening or a breakthrough of a dam sometimes caused by rapid erosion or a section of
earth embankment by water.
BUTTRESS DAM – A dam consisting of watertight upstream face supported at intervals on the
downstream side by a series of buttresses. Buttress dam can take many forms.
ARCH BUTTRESS DAM (BUTTRESS DAM) – A buttress dam that is curved in plan.
MULTIPLE ARCH DAM – A buttress dam, the upstream part of which comprises a series of arches.
FLAT SLAB DAM (AMBURSEN DAM) (DECK DAM) – A buttress dam is which the upstream part is a
relatively thin flat slab usually made of reinforced concrete.
- 65 -
SOLID HEAD BUTTRESS DAM – A buttress dam in which the upstream end of each buttress is
enlarged to span the gap between buttresses. The terms round head, diamond head and tee
head refer to the shape of the upstream enlargement.
CAVITATION – Wear on hydraulic structures where a high hydraulic gradient is present. Cavitation is
caused by the abrupt change in direction and velocity of the water so the pressure at some points
is reduced to the vapor pressure and vapor pockets are created. These pockets collapse with
great impact when they enter areas of higher pressure, producing very high impact pressures
over small areas that eventually cause pits and holes in the surface. Noises and vibrations may
be evident during high flows.
CONDUIT – A closed channel to convey the discharge through or under a dam.
CONSTRUCTION JOINT – The interface between two successive placings or pours of concrete where
bond, not permanent, separation is intended.
CORE (IMPERVIOUS CORE) (IMPERVIOUS ZONE) – A zone of material of low permeability in an
embankment dam; hence the terms central core, included core, puddle clay core and rolled clay
core.
COREWALL – A wall built of impervious material, usually of concrete or asphaltic concrete in the body of
an embankment dam to prevent leakage. See also Membrane or Diaphragm.
CREST LENGTH – The measured length of the top of the dam from abutment to abutment includes the
length of spillway, powerhouse, navigation lock, fish pass, etc., where these structures form part
of the length of the dam. If detached from the dam, these structures should not be included.
CREST OF DAM – The crown of an overflow section of the dam. In the United States, the term ''crest of
dam" is often used when °top of dam" is intended. To avoid confusion, the terms crest of spillway
and top of dam should be used for referring to the overflow section and dam proper, respectively.
CRIB DAM – A gravity dam built up of boxes, cribs, crossed timbers, or gabions and filled with earth or
rock.
CULVERT – (a) A drain or waterway structure built transversely under a road, railway, or embankment. A
culvert usually comprises a pipe or a covered channel of box section. (b) A gallery or waterway
constructed through any type of dam, which is normally dry but is used occasionally for
discharging water; hence the terms scour culvert, drawoff culvert and spillway culvert.
CURTAIN –
GROUT CURTAIN (GROUT CUTOFF) – A barrier produced by injecting grout into a vertical zone, usually
narrow in horizontal width, in the foundation to reduce seepage under a dam.
DRAINAGE CURTAIN – See Drainage Wells.
CUTOFF – An impervious barrier used to reduce or prevent seepage from passing through the foundation
under the dam.
CUTOFF TRENCH – The excavation later to be filled with impervious material so as to from the cutoff.
Sometimes used incorrectly to describe the cutoff itself.
CUTOFF WALL – A wall of impervious material (e.g., concrete, asphaltic concrete, steel sheet piling) built
into the foundation to reduce seepage under the dam.
DAM – A barrier built across a watercourse for impounding or diverting the flow of water. DESIGN
FLOOD – See Spillway Design Flood.
DIKE (LEVEE) – A long low embankment. The height is usually less than 4 to 5 meters and the length
more than 10 to 15 times the maximum height. Usually applied to embankments or structures
built to protect land from flooding. If built of concrete or masonry is usually referred to as a flood
wall. Also used to describe embankments that block areas on the reservoir dam rim that are lower
than the top of the main dam and that are quite long.
- 66 -
DIVERSON CHANNEL CANAL OR TUNNEL – A waterway used to divert water from its natural course.
The term is generally applied to a temporary arrangement, e.g., to bypass water around a dam
site during construction. Channel is normally used instead of canal when the waterway is short.
Occasionally the term is applied to a permanent arrangement (diversion canal, diversion tunnel,
diversion aqueducts).
DRAINAGE AREA – The area that drains naturally to a particular point on a river.
DRAINAGE LAYER OR BLANKET – A layer of pervious material in a dam to relieve pore pressures or to
facilitate drainage of the fill.
DRAINAGE WELLS (RELIEF WELLS) – Vertical wells or boreholes usually downstream of impervious
cores, grout curtains or cutoffs, designed to collect and control seepage through or under a dam
so as to reduce uplift pressures under or within a dam. A line of such wells forms a drainage
curtain.
DRAWDOWN – The resultant lowering of water surface level due to release of water from the reservoir.
EARTH DAM OR EARTHFILL DAM – See Embankment Dam.
EMBANKMENT – Fill material, usually earth or rock, placed with sloping sides.
EMBANKMENT-ABUTMENT CONTACT – See Groin.
EMBANKMENT DAM – Any dam constructed of excavated natural materials,
EARTH DAM (EARTHFILL DAM) – An embankment dam in which more than 50 percent of the total
volume is formed of compacted fine-grained material obtained from a borrow area.
HOMOGENEOUS EARTHFILL DAM – An embankment dam constructed of similar earth material
throughout, except for possible inclusion of internal drains or drainage blankets. Used to
differentiate from a zone earthfill dam.
HYDRAULIC FILL DAM – An embankment dam constructed of materials, often dredged, that are
conveyed and placed by suspension in flowing water.
ROCKFILL DAM – An embankment dam in which more than 50 percent of the total volume comprises
compacted or dumped pervious natural or crushed rock.
ROLLED FILL DAM – An embankment dam of earth or rock in which the material is placed in layers
and compacted by using rollers or rolling equipment.
ZONED EMBANKMENT DAM – An embankment dam, the thickness of which is composed of zones of
selected materials having different degrees of porosity, permeability and density.
EMERGENCY GATE – A standby or reservoir gate used only when the normal means of water control is
not available.
EMERGENCY SPILLWAY – See Spillway.
ENERGY DISSIPATOR – Any device constructed in a waterway to reduce or destroy the energy of fastflowing water.
FACE – With reference to a structure, the external surface that limits the structure, e.g., the face of a wall
or dam.
FAILURE – An incident resulting in the uncontrolled release of water from an operating dam.
FILTER (FILTER ZONE) – A band or zone of granule material that is incorporated in a dam and is graded
(either naturally or by selection) so as to allow seepage to flow across or down the filter without
causing the migration of material from zones adjacent to the filter.
FINGER DRAINS – A series of parallel drains of narrow width (instead of a continuous drainage blanket)
draining to the downstream toe of the embankment dam.
- 67 -
FLASHBOARDS – Lengths of timber or steel placed on the crest of a spillway to raise the retention water
level but that may be quickly removed in the event of a flood either by a tripping device or by
deliberately designed failure of the flashboards or their supports.
FLOOD PLAIN – An area adjoining a body of water or natural stream that has been or may be covered by
flood water.
FLOOD ROUTING – The determination of the attenuating effect of storage on a flood passing through a
valley, channel or reservoir.
FOUNDATION OF DAM – The natural material on which the dam structure is placed.
FREEBOARD – The vertical distance between a stated water level and the top of a dam.
FUSE PLUG SPILLWAY – See Spillway.
GABION – A prefabricated basket or rock within a wire cage that is free drainage and capable of being
stacked.
GABION DAM – Name given to a crib dam when built of gabions.
GATE – In general, a device in which a leaf or member is moved across the waterway from an external
position to control or stop the flow.
GRADIENT – The rate at which energy is dissipated by virtue of water movement through the soil.
GRAVITY DAM – A dam constructed of concrete and/or masonry that relies on its weight for stability.
ARCH GRAVITY DAM – An arch dam where part of the water thrust is transmitted to the abutments
by horizontal thrust and part to the foundation by cantilever action.
CURVED GRAVITY DAM – A gravity dam that is curved in plan.
HOLLOW GRAVITY DAM (CELLULAR GRAVITY DAM) – A dam that has the outward appearance of
a gravity dam but that is of hollow construction.
GROIN – That area along the contact (or intersection) of the face of a dam with the abutments.
GROUT A thin cement mortar used to fill voids, fractures or joints in masonry, rock, sand and gravel, and
other materials. As a verb it refers to filling voids with grout. Grout is usually applied under
pressure.
HEEL OF DAM — The junction of the upstream face of a gravity or arch dam with the foundation surface.
In the case of an embankment dam, the junction is referred to as the upstream toe of the dam.
HEIGHT OF DAM — The vertical measurement expressed in feet as measured from the downstream toe
of the dam at its lowest point to the elevation of the top of the dam.
HYDRAULIC HEIGHT — Height to which the water rises behind a dam and the difference between the
lowest point in the original streambed at the upstream toe of the dam and the maximum
controllable water surface.
HYDROGRAPH — A graphical representation of discharge, stage or other hydraulic property with respect
to time for a particular point on a stream.
IMPERVIOUS CORE — See Core.
INCLINOMETER (INCLOMETER) — An instrument, usually comprising of a metal or plastic tube inserted
in a drill hole, and sensitized monitor either lowered into the tube or fixed within the tube. The
instrument is used to measure slope movements at various depths below the ground surface.
INTAKE — Any structure in a reservoir, dam, or river through which water can be drawn into an aqueduct.
INTERNAL EROSION — See Piping.
INUNDATION MAP — A map delineating the area that would be inundated in the event of a dam failure.
LEFT ABUTMENT — The abutment on the left-hand side of an observer when looking downstream.
- 68 -
LEVEE — See Dike.
MASONRY DAM — Any dam constructed mainly of stone, brick or concrete blocks that may or may not
be jointed with mortar. A dam having only a masonry facing should not be referred to as a
masonry dam.
MAXIMUM CROSS SECTION OF DAM — Cross section of a dam at the point where the height of the
dam is a maximum.
MAXIMUM WATER LEVEL The maximum water level, including the flood surcharge the dam is designed
to withstand.
MEMBRANE (DIAPHRAGM) — A sheet or thin zone or facing made of a flexible impervious material such
as asphaltic concrete, plastic concrete, steel, wood, copper, plastic, etc. A cutoff wall, or core
well, if thin and flexible, is sometimes referred to as a diaphragm wall or diaphragm.
MORNING GLORY SPILLWAY — See Spillway.
NORMAL WATER LEVEL (NORMAL POOL) — For a reservoir with a fixed overflow spillway crest, it is
the lowest level of that crest.
OBSERVATION WELL — Small diameter perforated vertical tube installed within an embankment. Used
to measure the height of the internal water surface in the embankment at the location of the well.
OGEE SPILLWAY — See Spillway.
ONE-HUNDRED YEAR (100-YEAR) FLOOD – The flood magnitude expected to be equaled or exceeded
on the average of once in 100 years. It may also be expressed as an exceedance frequency with
a one percent change of being exceeded in any given year.
OUTLET – An opening through which water can be freely discharged for a particular purpose from a
reservoir.
OVERFLOW DAM (OVERTOPPABLE DAM) – A dam designed to be overtopped without failing.
OWNER – any person who owns, controls, operates, maintains or manages a dam or reservoir, water
obstruction or encroachment.
PERMEABILITY – A material property which defines the capacity to transmit water.
PERVIOUS ZONE – A part of the cross section of an embankment dam comprising material of high
permeability.
PHREATIC SURFACE – The free surface of water within an earth or rockfill dam.
PIEZOMETER – An instrument for measuring pore water pressure within soil, rock or concrete.
PIPING – The progressive development of internal erosion by seepage, appearing downstream as a hole
or seam discharging water that contains soil particles.
PLUNGE BASIN (PLUNGE POOL) – A natural or sometimes artificially created pool that dissipates the
energy of free-falling water. The basin is located at a safe distance downstream of the structure
from which water is being released.
PORE PRESSURE – The internal cellular pressure of water within a mass of soil, rock or concrete.
PROBABLE MAXIMUM PRECIPITATION (PMP) – The maximum amount and duration of precipitation
that can be expected to occur on a drainage basin.
PROBABLE MAXIMUM FLOOD (PMF) – The flood that may be expected from the most severe
combination of critical meteorological and hydrologic conditions that are possible in the region.
RANDOM FILL – Earth or rockfill, the grading of which is not specified and that is placed without
treatment just as it comes from the excavation.
RELIEF WELLS – See Drainage Wells.
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RIGHT ABUTMENT – The abutment on the right-handed side of an observer when looking downstream.
RIPRAP – A layer of large uncoursed stones, broken rock, or precast blocks placed in random fashion on
the upstream slope of an embankment dam, on a reservoir shore, or on the sides of a channel as
protection against wave and ice action.
ROCK FILL DAM – See Embankment Dam.
SADDLE DAM – A subsidiary dam of any type constructed across a saddle or low point on the perimeter
of a reservoir.
SCARP – The nearly vertical, exposed earth surface created at the upper edge of a slide or a beached
area along the upstream slope
SEEPAGE – The movement of water that may take place through the dam, its foundation or its
abutments.
SEEPAGE COLLAR – A projecting collar, usually of concrete, built around the outside of a pipe, tunnel or
conduit, under an embankment dam, to lengthen the seepage path along the outer surface of the
conduit. Sometimes referred to as "anti-seepage collar.
SEMI-IMPERVIOUS ZONE – A zone of relatively low permeability. See Transition Zone.
SHELL – The upstream and downstream parts of the cross section of a zoned embankment dam on each
side of the core or core wall.
SLIDE – The movement of a mass of earth and/or down a slope. In embankments and abutments, this
involves the separation of a portion of the slope from the surrounding material.
SPILLWAY – A structure over or through which flood flows are discharged. If the flow is controlled by
gates, it is considered a controlled spillway, if the elevation of the spillway crest is the only
control, it is considered an uncontrolled spillway.
AUXILIARY SPILLWAY (EMERGENCY SPILLWAY) – A secondary spillway designed to operate only
during exceptionally large floods.
FUSE PLUG SPILLWAY – A form of auxiliary or emergency spillway comprising a low embankment
or a natural saddle designed to be overtopped and eroded away during a very rare and
exceptionally large flood.
MORNING GLORY SPILLWAY – See Shaft Spillway.
OGEE SPILLWAY (OGEE SECTION) – An overflow weir in which in cross section the crest,
downstream slope and bucket have an S or ogee form of curve. The shape is intended to
match the underside of the nape at its upper extremities.
PRIMARY SPILLWAY (PRINCIPAL SPILLWAY) – The principal or first-used spillway during
floodflows.
SADDLE SPILLWAY – A spillway constructed at a low saddle on the perimeter of a reservoir.
SERVICE SPILLWAY A principal spillway used to regulate reservoir releases additional to or in lieu of
the outlet.
SHAFT SPILLWAY (MORNING GLORY SPILLWAY) – A vertical or inclined shaft into which flood
water spills and then is conducted through, under or around a dam by means of a conduit or
tunnel. If the upper part of the shaft is splayed out and terminates in a circular horizontal weir,
it is termed a bellmouth or morning glory spillway.
SIDE CHANNEL SPILLWAY – A spillway, the crest of which is roughly parallel to the channel
immediately downstream of the spillway.
SIPHON SPILLWAY – A spillway with one or more siphons built at crest level. This type of spillway is
sometimes used for providing automatic surface-level regulation within narrow limits or when
considerable discharge capacity is necessary within a short period of time.
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SPILLWAY CHANNEL – A channel conveying water from the spillway crest to the river downstream.
SPILLWAY CHUTE – A sloping spillway channel.
SPILLWAY DESIGN 'FLOOD (SDF) – The largest flood that a given project is designed to pass safely.
The reservoir inflow discharge hydrograph used to estimate the spillway discharge capacity
requirements and corresponding maximum surcharge elevation in the reservoir.
STAFF GAUGE – A device marked in feet used to indicate and measure water levels.
STILLING BASIN – A basin constructed to dissipate the energy of fast-flowing water, e.g., from a spillway
or bottom outlet, and to protect the river bed from erosion.
STOPLOGS– Large logs or timbers or steel beams placed on top of each other with their ends held in
guides on each side of a channel or conduit to provide a cheaper or more easily handled means
of temporary closure than a bulkhead gate.
STORAGE – The retention of water or delay of runoff either by planned operation, as in a 'reservoir, or by
temporary filling of overflow areas, as in the progression of a flood crest through a natural stream
channel.
SURVEY MONUMENT – A point established on or in the vicinity of an embankment. Provides a set point
to survey and, over time, will indicate whether any movement has taken place.
TAILWATER LEVEL – The level of water in the discharge channel immediately downstream of the dam.
TOE OF DAM – The junction of the downstream face of a dam with the ground surface. Also referred to
as downstream toe. For an embankment dam, the junction of the upstream face with a ground
surface is called the upstream toe.
TOP OF DAM – The elevation of the uppermost surface of a dam, usually a road or walkway, excluding
any parapet wall, railings, etc.
TOP WIDTH (TOP THICKNESS) – The thickness or width of a dam at the level of the top of the dam. In
general, the term thickness is used for gravity and arch dams and width is used for other dams.
TRANSITION ZONE (SEMI-IMPERVIOUS ZONE) – A part of the cross section of a zoned embankment
dam comprising material whose grading is of intermediate size between that of an impervious
zone and that of a permeable zone.
TRASH RACK – A screen comprising metal or reinforced concrete bars located in the waterway at an
intake to prevent the ingress of floating or submerged debris.
UNDERSEEPAGE (FOUNDATION SEEPAGE) – The movement of water through a foundation.
UPLIFT – (a) The upward water pressure on the base of a structure. (b) An upstream force on a structure
caused by frost heave or wind force.
VALVE – A device fitted to a pipeline or orifice in which the closure member is either rotated or moved
transversely or longitudinally in the waterway to control or stop the flow.
VOLUME OF DAM – The total space occupied by the materials forming the dam structure computed
between abutments and from the top to the bottom of a dam.
WATERSHED DIVIDE– The divide or boundary between drainage areas.
WEIR – A low dam or wall built across a stream to raise the upstream water level. Termed fixed-crest weir
when uncontrolled. A structure built across a stream or channel for the purpose of measuring
flow. Sometimes described as measuring weir or gauging weir. Types of weir include
broadcrested weir, shaped-crested weir, ogee weir and V-notched weir.
ZONED EARTHFILL – See Embankment Dam.
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APPENDIX E
SUBJECT INDEX
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SUBJECT INDEX
Page
Abutment Leakage or Seepage
20
Boil
Bulging
20
19
Concrete
Cracking
Deterioration
Inspection Items
Cracks or Cracking
In Concrete
In Soil
Crest Misalignment
Crest Settlement
28
28
29
28
14
28
14
14
15
Debris
Outlet Gate
Spillway
21
24
21
Embankment
Inspection
Maintenance
Embankment-Abutment Contact
Emergency Action Plan
Erosion
Adjacent to Outlet Conduit
At Embankment-Abutment Contact
Behind Riprap
Downstream Face
Spillway Channel
12
12
33
17
43
16
26
19
16
20
21
Failures
Hydraulic
Seepage
Structural
3
3
3
4
Hazard Potential
Category I, II, and III
43
Inspection
Checklists
Checklist Form
Embankment
Abutment and Foundation
Crest
Downstream slope
Upstream Slope
Equipment
Miscellaneous Areas
Concrete and Concrete Dams
Metalwork
Monitoring Devices
Reservoir
Outlet Works
Pennsylvania Requirements
Photographs
Preparation
Records
Spillway
Erodible Channels
Non-erodible Channels
8
31
51
12
20
14
18
16
9
27
28
28
27
27
24
8
31
9
31
21
21
22
Page
Maintenance
Embankment
Instructions
Items
Access Roads
Concrete
Conduit
Earthwork
Electrical
Hydraulic
Mechanical
Monitoring Devices
Rodent Control
Vandalism Prevention
Vegetation Control
Winterizing
Miscellaneous
Outlet Conduit
Records
Schedule
Spillway
33
33
42
34
38
36
36
36
37
37
36
38
34
39
34
39
34
34
39
39
33
Metalwork
Inspection Items
28
28
Monitoring Devices
Inclinometers
Inspection Items
Maintenance Items
Observation Wells
Piezometer
Survey Monuments
Weirs
4
5
27
38
5
38
5
6
Operations Plan
Outlet Works
Control Works Damage
Inspection Items
Maintenance
Pipe Damage
Valve Leakage
41
24
25
24
34
24
24
Pennsylvania Inspection Requirements
Puddling on Crest
8
15
Reservoir Slopes
Riprap
Broken Down or Deteriorated
Erosion Behind
Rodent Control
Ruts on Crest
11
16
16
16
34
15
Seepage and/or Leakage
Abutment
Clear
Concrete Dam
Concrete Spillway
Exiting as a Boil in the Foundation
Muddy
Outlet Conduit
Sinkholes, Depressions, Animal Burrow
18
20
18
30
23
20
18
26
15
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Page
Slide, Slump or Slip
Downstream Slopes
Reservoir Slopes
Spillway slopes
Upstream Slopes
Spillway
Inspection Items
Maintenance
16
19
27
21
16
21
21
33
Trash Rack
36
Vegetation
Control
Excessive
20
34
20
Whirlpool
17
Commonwealth of Pennsylvania
Department of Environmental Protection
An Equal Opportunity Employer
3140-BK-DEP2139
Rev. 3/2015
For more information, visit www.dep.state.pa.us, keyword: Dam Safety.
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