[Code of Federal Regulations]
[Title 33, Volume 3]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 33CFR222.6]
[Page 257-311]
TITLE 33--NAVIGATION AND NAVIGABLE WATERS
CHAPTER II--CORPS OF ENGINEERS, DEPARTMENT OF THE ARMY, DEPARTMENT OF
DEFENSE
PART 222_ENGINEERING AND DESIGN--Table of Contents
Sec. 222.6 National Program for Inspection of Non-Federal Dams.
(a) Purpose. This regulation states objectives, assigns
responsibilities and prescribes procedures for implementation of a
National Program for Inspection of Non-Federal Dams.
(b) Applicability. This regulation is applicable to all Divisions
and Districts having Civil Works functions.
(c) References. (1) The National Dam Inspection Act, Pub. L. 92-367,
8 August 1972.
(2) Freedom of Information Act, Pub. L. 87-487, 4 July 1967.
(3) ER 500-1-1.
(d) Authority. The National Dam Inspection Act, Public Law 92-367, 8
August 1972 authorizes the Secretary of the Army, acting through the
Chief of Engineers, to carry out a national program of inspection of
non-Federal dams for the purpose of protecting human life and property.
(e) Scope. The program provides for:
(1) An update of the National Inventory of Dams.
(2) Inspection of the following non-Federal dams (the indicated
hazard potential categories are based upon the location of the dams
relative to developed areas):
(i) Dams which are in the high hazard potential category (located on
Federal and non-Federal lands).
(ii) Dams in the significant hazard potential category believed by
the State to represent an immediate danger to the public safety due to
the actual condition of the dam.
(iii) Dams in the significant hazard potential category located on
Federal lands.
(iv) Specifically excluded from the national inspection program are:
(A) Dams under the jurisdiction of the Bureau of Reclamation, the
Tennessee Valley Authority, the International Boundary and Water
Commission and the Corps of Engineers and
(B) Dams which have been constructed pursuant to licenses issued
under the authority of the Federal Power Act, and
(C) Dams which have been inspected within the 12-month period
immediately prior to the enactment of this act by a State agency and
which the Governor of such State requests be excluded from inspection.
(f) Objectives. The objectives of the program are:
(1) To update the National Inventory of Dams by 30 September 1980.
(2) To perform the initial technical inspection and evaluation of
the non-Federal dams described in paragraph 222.8(e) of this section to
identify conditions which constitute a danger to human life or property
as a means of expediting the correction of hazardous conditions by non-
Federal interests. The inspection and evaluation is to be completed by
30 September 1981.
(3) To obtain additional information and experience that may be
useful in determining if further Federal actions are necessary to assure
national dam safety.
(4) Encourage the States to establish effective dam safety programs
for non-Federal dams by 30 September 1981 and assist the States in the
development of the technical capability to carry out such a program.
(g) Program execution--(1) Responsibilities. (i) The owner has the
basic legal responsibility for potential hazards created by their
dam(s). Phase II studies, as described in Chapter 4, Appendix D, and
remedial actions are the owner's responsibility.
(ii) The State has the basic responsibility for the protection of
the life and property of its citizens. Once a dam has been determined to
be unsafe, it is the State's responsibility to see that timely remedial
actions are taken.
(iii) The Corps of Engineers has the responsibility for executing
the national program. The Federal program for inspection of dams does
not modify the basic responsibilities of the States or dam owners. The
Engineering Division of the Civil Works Directorate is responsible for
overall program goals, guidance, technical criteria for inspections and
inventory and headquarters level coordination with other agencies. The
Water Resources Support Center (WRSC) located at Kingman Building, Fort
Belvoir, Virginia 22060 is responsible for:
(A) Program Coordination of both the inventory and inspection
programs.
[[Page 258]]
(B) Developing and defining functional tasks to achieve program
objectives.
(C) Determining resource requirements. (Budget)
(D) Compiling and disseminating progress reports.
(E) Monitoring and evaluating program progress and recommending
corrective measures as needed.
(F) Collecting and evaluating data pertaining to inspection reports,
dam owners' responses to inspection report recommendations, attitudes
and capabilities of State officials, State dam safety legislation,
Architect-Engineer performance, etc., for defining a comprehensive
national dam safety program.
(G) Responding to Congressional, media, scientific and engineering
organization and general public inquiries.
Division and District offices are responsible for executing the program
at the State level. Assignment of Division reponsibilities for States is
shown in Appendix A.
(2) State participation. Where State capability exists, every effort
should be made to encourage the State to execute the inspection program
either with State personnel or with Architect-Engineer (A-E) contracts
under State supervision. If the State does not have the capability to
carry out the inspection program, the program will be managed by the
Corps of Engineers utilizing Corps employees or contracts with A-E firm.
(h) Update of National Inventory of Dams. (RCS-DAEN-CWE-17/OMB No.
49-RO421)
(1) The National Inventory of Dams should be updated and verified to
include all Federal and non-Federal dams covered by the Act. Those dams
are defined as all artificial barriers together with appurtenant works
which impound or divert water and which: (1) Are twenty-five feet or
more in height or (2) have an impounding capacity of fifty acre-feet or
more. Barriers which are six feet or less in height, regardless of
storage capacity or barriers which have a storage capacity at maximum
water storage elevation of fifteen acre-feet or less regardless of
height are not included.
(2) Inventory data for all dams shall be provided in accordance with
Appendix B.
(3) The hazard potential classification shall be in accordance with
paragraph 2.1.2 Hazard Potential of the Recommended Guideline for Safety
Inspection of Dams (Appendix D to this section).
Table 2--Hazard Potential Classification
----------------------------------------------------------------------------------------------------------------
Category Urban development Economic loss
----------------------------------------------------------------------------------------------------------------
Low.................................... No permanent structure for human Minimal (Undeveloped to occasional
habitation. structures or agriculture).
Significant............................ No urban development and no more Appreciable (Notable agriculture,
than a small number of habitable industry or structures).
structures.
High................................... Urban development with more than a Excessive (Extensive community,
small number of habitable industry or agriculture).
structures.
----------------------------------------------------------------------------------------------------------------
(4) As in the original development of the inventory, the States
should be encouraged to participate in the work of completing, verifying
and updating the inventory. Also, when available, personnel of other
appropriate Federal agencies should be utilized for the inventory work
on a reimbursable basis. Work in any State may be accomplished:
(i) Under State supervision utilizing State personnel or Architect-
Engineers contracts.
(ii) Under Corps supervision utilizing Corps employees, employees of
other Federal agencies or Architect-Engineer contracts.
(5) A minimum staff should be assigned in Districts and Divisions to
administer and monitor the inventory activities. Generally, the work
should be accomplished by architect-engineers or other Federal agency
personnel under State or Corps supervision. Corps personnel should
participate in the inventory only to the extent needed to assure that
accurate data are collected.
[[Page 259]]
(6) The National Inventory of Dams computerized data base in stored
on the Boeing Computer Services (BCS) EKS computer system in Seattle,
Washington. The data base uses Data Base Management System 2000 and is
accessible for query by all Corps offices.
(7) Appendix B indicates details on accessing and updating inventory
data.
(8) Appendix I describes the procedure for using NASA Land Satellite
(LANDSAT) Multispectral Scanner data along with NASA's Surface Water
Detection and Mapping (DAM) computer program to assist in updating and
verifying and National Inventory of Dams.
(9) All inventory data for dams will be completed and verified
utilizing all available sources of information (including LANDSAT
overlay maps) and will include site visitation if required. It is the
responsibility of the District Engineer to insure that the inventory of
each State within his area of responsibility is accurate and contains
the information required by the General Instructions for completing the
forms for each Federal and non-Federal dam.
(i) [Reserved]
(j) Inspection Program. (RCS-DAEN-CWE-17 and OMB No. 49-RO421)
(1) Scheduling of inspections. The Governor of each State or his
designee will continue to be involved in the selection and scheduling of
the dams to be inspected. Priority will be given to inspection of those
dams considered to offer the greatest potential threat to public safety.
(i) No inspection of a dam should be initiated until the hazard
potential classification of the dam has been verified to the
satisfaction of the Corps. Dams in the significant hazard category
should be inspected only if requested by the State and only then if the
State can provide information to show that the dam has deficiencies that
pose an immediate danger to the public safety. Guidance for the
selection of significant category non-Federal dams on Federal lands will
be given in the near future.
(ii) Selection for inspection of non-Federal dams located on Federal
lands or non-Federal dams designed and constructed under the
jurisdiction of some Federal agency, should be coordinated with the
responsible Federal agency. The appropriate State or regional
representative of the Federal agency also should be contacted to obtain
all available data on the dam. Representatives of the agency may
participate in the inspection if they desire and should be given the
opportunity to review and comment on the findings and recommendations in
the inspection report prior to submission to the Governor and the dam
owner. Examples of such dams are: non-Federal dams built on lands
managed by National Forest Service, Bureau of Land Management, Fish and
Wildlife Service, etc.; non-Federal dams designed and constructed by the
Soil Conservation Service of the U.S. Department of Agriculture; high
hazard mine tailings and coal mine waste dams under the jurisdiction of
the Mine Safety and Health Administration, Department of Labor.
(iii) Indian-owned dams on trust lands are considered to be non-
Federal dams. All dams in the high hazard potential category will be
inspected. Privately-owned dams located on Indian lands are to be
included in the program, however BIA-owned dams on Indian lands are
Federal dams and are exempt.
(2) Procedures. The Division Engineer is responsible for the quality
of inspections and reports prepared by the District Engineer. Close
liaison between the District Engineer and the State agency or A-E firm
responsible for the inspections will be required in order to obtain a
dependable result. To avoid undesirable delays in the evaluation of
safety of individual dams, contracts with A-E's or agreements with
States which are managing the program will provide that reports be
completed and furnished to the District Engineer within a specified time
after completion of the on-site inspection of the dam.
(i) Inspection guidelines. The inspection should be conducted in
accordance with the Recommended Guidelines for Safety Inspection of Dams
(Appendix D to this section). Expanded Guidance for Hydrologic and
Hydraulic Assessment of Dams is provided in Appendix C. The criteria in
the recommended guidelines are screening criteria to be used only
[[Page 260]]
for initial determinations of the adequacy of the dam. Conditions found
during the investigation which do not meet the guideline recommendations
should be assessed as to their importance from the standpoint of the
degree of risk involved.
(ii) Coordinators. Experience has shown that coordination and
communications among technical disciplines, Public Affairs Office,
emergency officials, training officers, operations personnel, State
representatives and A-E firms has been best in those districts where one
person was delegated the responsiblity for coordinating the actions of
all involved elements. Each district should evaluate its overall
coordination procedures to insure that all involved elements have the
best possible access to necessary data.
(iii) Field investigations should be carried out in a systematic
manner. A detailed checklist or inspection form should be developed and
used for each dam inspection and appended to the inspection report. The
size of the field inspection team should be as small as practicable,
generally consisting of only one representative of each required
discipline in order to control the costs of the inspection without
sacrificing the quality of the inspection. The inspection team for the
smaller less complex dams should be limited to two or three
representatives from appropriate technical areas with additional
specialists used only as special conditions warrant. The larger more
complex projects may require inspection teams of three or four
specialists. Performance of overly detailed and precise surveys and
mapping should be avoided. Necessary measurement of spillway, dam
slopes, etc. can generally be made with measuring tapes and hand levels.
(iv) Additional engineering studies. Dam inspections should be
limited to Phase I investigations as outlined in Chapter 3 of Appendix
D. However, if recommended by the investigating engineer and approved by
the District Engineer, some additional inexpensive investigations may be
performed when a reasonable judgment on the safety of the dam cannot be
made without additional investigation. Any further Phase II
investigation needed to prove or disprove the findings of the District
Engineer or to devise remedial measures to correct deficiencies are the
responsibility of the owner and will not be undertaken by the Corps of
Engineers.
(v) Assessment of the investigation. (A) The findings of the visual
inspection and review of existing engineering data for a dam shall be
assessed to determine its general condition. Dams assessed to be in
generally good condition should be so described in the inspection
report. Deficiencies found in a dam should be described and assessed as
to the degree of risk they present. The degree of risk should consider
only loss of life and/or property damage resulting from flooding due to
dam failure. Loss of project benefits i.e., municipal water supply,
etc., should not be considered. If deficiencies are assessed to be of
such a nature that, if not corrected, they could result in the failure
of the dam with subsequent loss of life and/or substantial property
damage, the dam should be assessed as ``Unsafe.'' If the probable
failure of an ``Unsafe'' dam is judged to be imminent and immediate
action is required to reduce or eliminate the hazard, the ``unsafe''
condition of the dam should be considered an ``emergency.'' If the
probable failure is judged not to be imminent, the ``unsafe'' condition
should be considered a ``non-emergency.''
(B) Adequacy of spillway. The ``Recommended Guidelines for Safety
Inspection of Dams,'' Appendix D, provide current, acceptable inspection
standards for spillway capacity. Any spillway capacity that does not
meet the criteria in the ``Guidelines'' is considered inadequate. When a
spillway's capacity is so deficient that it is seriously inadequate, the
project must be considered unsafe. If all of the following conditions
prevail, the Governor of the State shall be informed that such project
is unsafe:
(1) There is high hazard to loss of life from large flows downstream
of the dam.
(2) Dam failure resulting from overtopping would significantly
increase the hazard to loss of life downstream from the dam over that
which would exist just before overtopping failure.
[[Page 261]]
(3) The spillway is not capable of passing one-half of the probable
maximum flood without overtopping the dam and causing failure.
Classification of dams with seriously inadequate spillways as ``unsafe,
non-emergency'' is generally a proper designation of the urgency of the
unsafe condition. However, there may be cases where the spillway
capacity is unusually small and the consequences of dam overtopping and
failure would be catastrophic. In such cases, the unsafe dam should be
classified as an emergency situation.
(vi) All inspection reports will receive one level of independent
review by the Corps. If the reports are prepared by the Corps, the
independent review may be performed internally within the district
office. However, in cases which involve significant economic, social or
political impacts and technical uncertainties in evaluating the dams,
advice may be obtained from the staffs of the Division Engineer and the
Office, Chief of Engineers.
(3) Reports--(i) Preparation. A written report on the condition of
each dam should be prepared as soon as possible after the completion of
the field inspection and assessment. A suggested report format is
attached as Appendix E. It is important that the inspection report be
completed in a timely manner. For inspections being done by Corps
employees, it is suggested that once an inspection team has been
assigned to a dam inspection it be allowed to complete the inspection
and report without interruption by other work.
(ii) Review and approval. The coordinating engineer should determine
which disciplines should review the report and establish a procedure to
accomplish the review in a timely manner. A review panel, made up of the
appropriate Division and Branch Chiefs has worked well in some
districts. Use of a review panel should be seriously considered by all
districts. All inspection reports shall be approved by the District
Engineer who will maintain a complete file of final approved reports.
Any State or Federal agency having jurisdiction over the dam or the land
on which the dam is built should be given the opportunity to review and
comment on the report prior to submission to the Governor or dam owner.
The District Engineer will transmit final approved reports to the
Governor of the State and the dam owner (or the Governor only, when
requested in writing by State officials). If the report is initially
furnished to the Governor only, a period of up to ten days may be
allowed before the report is furnished to the dam owner. If the Governor
or the owner indicates additional technical information is available
that might affect the assessment of the dam's condition, the District
Engineer will furnish the proposed final report to the Governor and the
owner and establish a definite time period for comments to be furnished
to the District Engineer prior to report approval.
(iii) In general the Governor will be responsible for public release
of an inspection report and for initiating any public Statements.
However, an approved report must be treated as any other document
subject to release upon request under the Freedom of Information Act.
The letters of transmittal to the Governor and owner should indicate
that under the provisions of the Freedom of Information Act, the
documents will be subject to release upon request after receipt by the
Governor. Proposed final reports will be considered as internal working
papers not subject to release under the Freedom of Information Act.
Corps personnel, A-E contractor personnel and others working under
supervision of the Corps will be cautioned to avoid public statements
about the condition of the dam until after the District Engineer has
approved the report. The Corps will respond fully to inquiries after the
Governor has received the approved report or been notified of an unsafe
dam. An information copy of the report should be sent to the District
office normally having jurisdiction if other than the District
responsible for the inspection.
(iv) Follow-up action. A Federal investment of the magnitude
anticipated for this inspection program makes it desirable that a
reporting system be established to keep the District Engineer abreast of
the implementation of the recommendations in the inspection reports. The
letters of transmittal to the Governor and owner will request that
[[Page 262]]
the District Engineer be informed of the actions taken on the
recommendations in the inspection reports. However, the National Dam
Inspection Act only authorizes the initial inspection of certain dams;
therefore, once a report is completed no reinspection will be
undertaken.
(4) Unsafe dams. The investigating engineer will be required to
immediately notify the District Engineer when a dam is assessed as being
unsafe. He will also indicate if probable failure of the unsafe dam is
judged to be imminent and immediate action is required to reduce or
eliminate the threat. The District Engineer will evaluate the findings
of the investigating team and will immediately notify the Governor and
the owner if the findings are Unsafe Non-Emergency or Unsafe-Emergency.
The appropriate State agency and the Corps of Engineers officials having
emergency operation responsibility for the area in which the dam is
located will also be notified. The information provided in the unsafe
dam notice shall be as indicated in Appendix F. Any emergency procedures
or remedial actions deemed necessary by the District Engineer will be
recommended to the Governor who has the responsibility for any
corrective actions. As provided in ER 500-1-1, Corps assistance under
Pub. L. 84-99 ``Advance Measures,'' may be made available to complement
the owner's and Governor's action under certain conditions and subject
to the approval of the Director of Civil Works. The District Engineer's
Emergency Operation Officer will coordinate the advance measures request
in accordance with existing procedures. Coordination will be maintained
between the District responsible for emergency action under Pub. L. 84-
90 and the District responsible for the inspection.
(5) Emergency action plans. An emergency action plan should be
available for every dam in the high and significant hazard category.
Such plans should outline actions to be taken by the operator to
minimize downstream effects of an emergency and should include an
effective warning system. If an emergency action plan has not been
developed, the inspection report should recommend that the owner develop
such an action plan. However, the Corps has no authority to require an
emergency action plan.
(k) Progress reports. Progress reports should be submitted monthly
by the Division Engineer to WRSC. The reports shall include progress
through the last Saturday of the month and should be mailed by the
following Monday. The reports shall contain the information and be
typewritten in the format shown in Appendix G. Copies of Unsafe Dam Data
Sheets will be submitted with the progress report. Copies of the
completed inspection report for Dams in the Unsafe-Emergency category
will be submitted also. (RCS-DAEN-CWE-19)
(l) Contracts--(1) Corps of Engineers supervision. Contracts for
performing inventory and inspection activities under supervision of the
Corps of Engineers shall be Fixed-Price Architect Engineer Contracts for
Services. A sample scope of work setting forth requirements is provided
in Appendix H. Experience has shown that costs for individual dam
inspection have been lower when multiple inspections are included in one
contract. Therefore, each A-E contract should include multiple dam
inspections where practicable. Corps participation in A-E inspections
should be held to a minimum. Corps representatives should participate in
only enough A-E inspections to assure the equality of the inspections.
(2) State supervision. Contracts with States for performing
inventory and inspection activities under State supervision may be
either a Cost-Reimbursement type A-E Contract for Services or a Fixed-
Price type contract. The selection of Architect-Engineers by the State
should require approval of the Corps of Engineers Contracting Officer.
The negotiated price for A-E services under cost-reimbursement type
contracts with States will also require approval by the Contracting
Officer. Contracts with States should require timely submission of the
inspection reports to the District Engineer for review and approval. The
contract provisions should also prevent public release of or public
comment on the inspection report until the District Engineer has
reviewed and approved the report. Corps
[[Page 263]]
of Engineers participation in State inspections should be limited to
occasional selected inspections to assure the quality of the State
program.
(m) Training. As indicated in paragraph (f) of this section, one
objective of the inspection program for non-Federal Dams is to prepare
the States to provide effective dam safety programs. In many States this
will require training of personnel of State agencies in the technical
aspects of dam inspections. The Office, Chief of Engineers is studying
the need for and content of a comprehensive Corps-sponsored training
program in dam inspection technology. Pending the possible adoption of
such a comprehensive plan, division and district Engineers are
encouraged to take advantage of suitable opportunities to provide needed
training in dam safety activities to qualified employees of State
agencies and, when appropriate, to employees of architect-engineer firms
engaged in the program. The following general considerations should be
observed in providing such training:
(1) Priority must be placed on inspection of dams and updating the
national dam inventory; hence, diversion of resources to training
activities should not deter or delay these principle program functions.
(2) Salaries, per diem and travel expenses relating to training
activities of State employees will be a State expense. There will be no
tuition charge for State employees.
(3) Architect-Engineer firms will be required to pay expenses and
tuition costs for their employees participating in Corps-sponsored
training activities.
(4) Corps-sponsored training will require that each trainee is a
qualified engineer or geologist and will concentrate on engineering
technology related directly to dam safety. (This may require screening
of proposed candidates for training.)
(5) Under this program, the Corps will not sponsor training that is
intended primarily to satisfy requirements for a degree.
(6) Training by participation in actual dam inspections and/or
management of the inspection program should be encouraged.
Appendix A to Sec. 222.6--Division Assignments
To facilitate better coordination with the States, the Division
Engineers are responsible for the dam inspection program by States as
follows:
New England Division: Maine, Rhode Island, Connecticut, Vermont, New
Hampshire, Massachusetts
North Atlantic Division: New York, New Jersey, Pennsylvania, Delaware,
Maryland, Virginia, District of Columbia
Ohio River Division: West Virginia, Ohio, Kentucky, Tennessee, Indiana
South Atlantic Division: North Carolina, South Carolina, Georgia,
Florida, Alabama, Puerto Rico, Virgin Islands
Lower Mississippi Valley Division: Mississippi, Louisiana, Missouri
North Central Division: Michigan, Wisconsin, Illinois, Minnesota, Iowa
Southwestern Division: Arkansas, Oklahoma, Texas, New Mexico
Missouri River Division: Kansas, Nebraska, South Dakota, North Dakota,
Wyoming, Colorado
North Pacific Division: Oregon, Idaho, Montana, Washington, Alaska
South Pacific Division: Utah, California, Arizona, Nevada
Pacific Ocean Division: Hawaii, Trust Territories, American Samoa
Appendix B to Sec. 222.6--Inventory of Dams
(RCS-DAEN-CWE-17 and OMB No. 49-RO421)
1. The updating of the inventory will include the completion of all
items of data for all dams now included in the inventory, verification
of the data now included in the inventory, and inclusion of complete
data for all appropriate existing dams not previously listed. Data
completion, verification and updating will be scheduled over a three
year period.
2. The inventory data will be recorded on Engineering Form 4474 and
4474A (Exhibit 2). The general instructions for completing the forms are
printed on the back of the forms. Parts I and II of the forms are to be
fully completed. The instruction for completing Item 29, Line 5, Para.
II (Engr Form 4474A) is revised to conform identically with the hazard
potential classification contained in the recommended guidelines for
safety inspection of dams. Additional data has been added to designate
Corps districts in which the dam is located, Federal agency owned dams,
Corps owned dams, Federal agency regulated dams, dams constructed with
technical or financial assistance of the U.S. Soil Conservation Service,
and privately owned dams located on Federal property.
3. All inventory data will be verified utilizing all available
sources of information and will include site visitation if required.
[[Page 264]]
4. The Inventory Data Base is stored on the Boeing Computer Services
(BCS) EKS System in Seattle, Washington. The data is available to all
Corps offices for queries using Data Base Management System 2000 (S2K).
a. To access the National Data Base log on BCS and type the
following:
GET,DAMS/UN=CECELB
CALL,DAMS
b. For current information and changes to the National Inventory
Data Base, type:
OLD,HOTDAM/UN=CEC1AT
LIST
5. The inventory update data will be furnished and the National Data
Base will be updated on a monthly basis. The monthly submission will
cover all dams whose inventory data were completed since the last
report. The update data will be loaded directly onto the Boeing Computer
by the field office.
a. The procedure for loading the data on the Boeing Computer can be
printed by accessing the Boeing Computer and listing the information
file ``HOTDAM.'' (See paragraph 4b. above.)
b. It is the responsibility of the submitting office to edit the
data prior to furnishing it for the update. Editing will be accomplished
by processing the data using the Inventory Edit Computer program
developed by the Kansas City District. This procedure is described in
the ``HOTDAM'' file.
6. Federal agencies will be uniformly designated by major and minor
abbreviations according to the following list whenever applicable to
Items 46 through 53. Abbreviations are to be left justified within the
field with one blank separating major and minor abbreviations.
------------------------------------------------------------------------
Major Minor
------------------------------------------------------------------------
a. International Boundary and Water IBWC
Commission.
b. U.S. Department of Agriculture:
(1) Soil Conservation Service....... USDA SCS
(2) Forest Service.................. USDA FS
c. U.S. Department of Energy Federal DOE FERC
Energy Regulatory Commission.
d. Tennessee Valley Authority......... TVA
e. U.S. Department of Interior:
(1) Bureau of Sport Fisheries and DOI BSFW
Wildlife.
(2) Geological Survey............... DOI GS
(3) Bureau of Land Management....... DOI BLM
(4) Bureau of Reclamation........... DOI USBR
(5) Bureau of Indian Affairs........ DOI BIA
f. U.S. Department of Labor: (1) Mine DOL MSHA
Safety and Health Administration.
g. Corps of Engineers:
(1) Lower Mississippi Valley
Division:
(a) Memphis District.............. DAEN LMM
(b) New Orleans District.......... DAEN LMN
(c) St. Louis District............ DAEN LMS
(d) Vicksburg District............ DAEN LMK
(2) Missouri River Division:
(a) Kansas City District.......... DAEN MRK
(b) Omaha District................ DAEN MRO
(3) New England Division............ DAEN NED
(4) North Atlantic Division:........
(a) Baltimore District............ DAEN NAB
(b) New York District............. DAEN NAN
(c) Norfolk District.............. DAEN NAO
(d) Philadelphia District......... DAEN NAP
(5) North Central Division:
(a) Buffalo District.............. DAEN NCB
(b) Chicago District.............. DAEN NCC
(c) Detroit District.............. DAEN NCE
(d) Rock Island District.......... DAEN NCR
(e) St. Paul District............. DAEN NCS
(6) North Pacific Division:
(a) Alaska District............... DAEN NPA
(b) Portland District............. DAEN NPP
(c) Seattle District.............. DAEN NPS
(d) Walla Walla District.......... DAEN NPW
(7) Ohio River Division:
(a) Huntington District........... DAEN ORH
(b) Louisville District........... DAEN ORL
(c) Nashville District............ DAEN ORN
(d) Pittsburgh District........... DAEN ORP
(8) Pacific Ocean Division.......... DAEN POD
(9) South Atlantic Division:
(a) Charleston District........... DAEN SAC
(b) Jacksonville District......... DAEN SAJ
(c) Mobile District............... DAEN SAM
(d) Savannah District............. DAEN SAS
(e) Wilmington District........... DAEN SAW
(10) South Pacific Division:
(a) Los Angeles District.......... DAEN SPL
(b) Sacramento District........... DAEN SPK
(c) San Franciso District......... DAEN SPN
(11) Southwestern Division:
(a) Albuquerque District.......... DAEN SWA
(b) Fort Worth District........... DAEN SWF
(c) Galveston District............ DAEN SWG
(d) Little Rock District.......... DAEN SWL
(e) Tulsa District................ DAEN SWT
------------------------------------------------------------------------
7. Procedures for Revising and Updating the Inventory of Dams Master
File.
a. To Change Correct or Add an Item. Submit a change card that
contains the identification assigned to the dams (Columns 1 thru 7), the
proper card code (Column 80) and only the item or items changed,
corrected or added. Data on the master file is added or replaced on an
item for item basis.
b. To Delete an Item. Submit a change card that contains the
identification assigned to the dam, (Columns 1 thru 7), the proper card
code (Column 80), and an asterisk (*) in the left most column of the
item or items to be deleted. More than one item can be changed,
corrected, added on or deleted from the same card.
c. To Delete the Entire Data for a Dam from the Master File. Submit
a zero (0) card punched as follows:
Columns 1 thru 7--Item 1 identification assigned to the dam
Columns 8 thru 10--Item 2, Division Code
Columns 11 thru 16--The word DELETE
Columns 17 thru 79--Blank Spaces
Column 80--A zero
8. Keypunch Instructions and Punched Card Formats.
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a. Table 1 describes the character set to be used for keypunch cards
of Engr. Forms 4474 and 4474A.
b. Exhibit 1 is the EDPC keypunch instructions and punch card
formats defining the data fields (Items) and card columns to be used in
preparing punched cards in compliance with the requirements of this
regulation.
c. Exhibit 2 are prints of Engr. Forms 4474 and 4474A which are laid
out in punch card format to facilitate punching cards directly from the
completed forms.
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Appendix C to Sec. 222.6--Hydrologic and Hydraulic Assessment of Dams
1. Phase I inspections are not intended to provide detailed
hydrologic and hydraulic analyses of dam and reservoir capabilities.
However, when such analyses are available, they should be evaluated for
reliability and completeness. If a project's ability to pass the
appropriate flood (see Table 3, page D-12 of Recommended Guidelines) can
be determined from available information of a brief study, such an
assessment should be made. It should be noted that hydrologic and
hydraulic analyses connected with the Phase I inspections should be
based on approximate methods or systematized computer programs that take
minimal effort. The Hydrologic Engineering Center (HEC) has developed a
special computer program for hydrologic and hydraulic analyses to be
used with the Phase I inspection program. Other Field Operating Agencies
have developed similar computer programs or generalized procedures which
are acceptable for use. All such efforts should be completed with
minimum resources.
2. A finding that a dam will not safely pass the flood indicated in
the Recommended Guidelines does not necessarily indicate that the dam
should be classified as unsafe. The degree of inadequacy of the spillway
to pass the appropriate flood and the probable adverse impacts of dam
failure because of overtopping must be considered in making such
classification. The following criteria have
[[Page 277]]
been selected which indicate when spillway capacity is so seriously
inadequate that a project must be classified as unsafe. All of the
following conditions must prevail before designating a dam unsafe:
a. There is high hazard to loss of life from large flows downstream
of the dam.
b. Dam failure resulting from overtopping would significantly
increase the hazard to loss of life downstream from the dam from that
which would exist just before overtopping failure.
c. The spillway is not capable of passing one-half of the probable
maximum flood without overtopping the dam and causing failure.
3. The above criteria are generally adequate for evaluating most
non-Federal dams. However, in a few cases the increased hazard potential
from overtopping and failure is so great as to result in catastrophic
consequences. In such cases, the evaluation of condition 2c should
utilize a flood more closely approximating the full probable maximum
flood rather than one-half the flood. An example of such a situation
would be a large dam immediately above a highly populated flood plain,
with little likelihood of time for evacuation in the event of an
emergency.
4. Conditions 2a and 2b require an approximation of housing location
in relation to flooded areas. Resources available in Phase I inspections
do not permit detailed surveys or time-consuming studies to develop such
relationships. Therefore, rough estimates will generally be made from
data obtained during the inspection and from readily available maps and
drawings. Brief computer routings such as the HEC-1 dam break analysis,
using available data, are recommended in marginal cases. The HEC-1, dam
break version, is available on the Boeing Computer Services or may be
obtained from the Hydrologic Engineering Center, Davis, California.
Available resources do not permit detailed studies or investigations to
establish the amount of overtopping that would cause a dam to fail, as
designated in condition 2c. Professional judgment and available
information will have to be used in these determinations. When detailed
investigations and studies are required to make a reasonable judgment of
the conditions which designate an unsafe dam, the inspection report
should recommend that such studies be the responsibility of the dam
owner.
5. During the inspection of a dam, consideration should be given to
impacts on other dams located downstream from the project being
inspected. When failure of a dam would be likely to cause failure of
another dam(s) downstream, its designation as an unsafe dam could result
in multiple impacts. Therefore, the information should be explicitly
described in the inspection report. Such information may be vital to the
priorities established by State Governors for dam improvements.
Similarly, when the failure of an upstream dam (classified as unsafe)
could cause failure of the dam being inspected, this information should
be prominently displayed in the inspection report.
6. The criteria established in paragraph 2 for designating unsafe
dams because of seriously inadequate spillways are considered reasonable
and prudent. They provide a consistent bases for declaring unsafe dams
and also serve as an effective compromise between the Recommended
Guidelines and unduly low standards suggested by special interests and
individuals unfamiliar with flood hazard potential.
7. The Hydrometeorological Branch (HMB) of the National Weather
Service has reviewed some 500 experienced large storms in the United
States. The purpose of the review was to ascertain the relative
magnitude of experienced large storms to probable maximum precipitation
(PMP) and their distribution throughout the country. Their review
reveals that about 25 percent of the major storms have exceeded 50
percent of the probable maximum precipitation for one or more
combinations of area and duration. In fact some storms have very closely
approximated the PMP values. Exhibits C-1 thru C-5 indicate locations
where experienced storms have exceeded 50 percent of the PMP.
8. There are several options to consider when selecting mitigation
measures to avoid severe consequences of a dam failure from overtopping.
The following measures may be required by a Governor when sufficient
legal authority is available under State laws and a dam presents a
serious threat to loss of life.
a. Remove the dam.
b. Increase the height of dam and/or spillway size to pass the
probable maximum flood without overtopping the dam.
c. Purchase downstream land that would be adversely impacted by dam
failure and restrict human occupancy.
d. Enhance the stability of the dam to permit overtopping by the
probable maximum flood without failure.
e. Provide a highly reliable flood warning system (generally does
not prevent damage but avoids loss of life).
[[Page 278]]
Table 1--Storms With Rainfall =150% of PMP, U.S. East of the 105th Meridian (for 10 mi\2\, 6 Hours;
200 mi\2\, 24 Hours and/or 1,000 mi\2\, 48 Hours)
----------------------------------------------------------------------------------------------------------------
Corps assignment Storm center
Storm date Index No. (if ------------------------------------ Latitude Longitude
No. available) Town State
----------------------------------------------------------------------------------------------------------------
July 26, 1819................ 1 ................ Catskill........ NY.............. 42[deg]1 73[deg]53
2[min] [min]
Aug. 5, 1843................. 2 ................ Concordville.... PA.............. 39[deg]5 75[deg]32
3[min] [min]
Sept. 10-13, 1878............ 3 OR 9-19......... Jefferson....... OH.............. 41[deg]4 80[deg]46
5[min] [min]
Sept. 20-24, 1882............ 4 NA 1-3.......... Paterson........ NJ.............. 40[deg]5 74[deg]10
5[min] [min]
June 13-17, 1886............. 5 LMV 4-27........ Alexandria...... LA.............. 31[deg]1 92[deg]33
9[min] [min]
June 27-July 11, 1899........ 6 GM 3-4.......... Turnersville.... TX.............. 30[deg]5 96[deg]32
2[min] [min]
Aug. 24-28, 1903............. 7 MR 1-10......... Woodburn........ IA.............. 40[deg]5 93[deg]35
7[min] [min]
Oct. 7-11, 1903.............. 8 GL 4-9.......... Paterson........ NJ.............. 40[deg]5 74[deg]10
5[min] [min]
July 18-23, 1909............. 9 UMV 1-11B....... Ironwood........ MI.............. 46[deg]2 90[deg]11
7[min] [min]
July 18-23, 1909............. 10 UMV 1-11A....... Beaulieu........ MN.............. 47[deg]2 95[deg]48
1[min] [min]
July 22-23, 1911............. 11 ................ Swede Home...... NB.............. 40[deg]2 96[deg]54
2[min] [min]
July 19-24, 1912............. 12 GL 2-29......... Merrill......... WI.............. 45[deg]1 89[deg]41
1[min] [min]
July 13-17, 1916............. 13 SA 2-9.......... Altapass........ NC.............. 35[deg]3 82[deg]01
3[min] [min]
Sept. 8-10, 1921............. 14 GM 4-12......... Taylor.......... TX.............. 30[deg]3 97[deg]18
5[min] [min]
Oct. 4-11, 1924.............. 15 SA 4-20......... New Smyrna...... FL.............. 29[deg]0 80[deg]55
7[min] [min]
Sept. 17-19, 1926............ 16 MR 4-24......... Boyden.......... IA.............. 43[deg]1 96[deg]00
2[min] [min]
Mar. 11-16, 1929............. 17 UMV 2-20........ Elba............ AL.............. 31[deg]2 86[deg]04
5[min] [min]
June 30-July 2, 1932......... 18 GM 5-1.......... State Fish TX.............. 30[deg]0 99[deg]07
Hatchery. 1[min] [min]
Sept. 16-17, 1932............ 19 ................ Ripogenus Dam... ME.............. 45[deg]5 69[deg]09
3[min] [min]
July 22-27, 193.............. 20 LMV 2-26........ Logansport...... LA.............. 31[deg]5 94[deg]00
8[min] [min]
Apr. 3-4 1934................ 21 SW 2-11......... Cheyenne........ OK.............. 35[deg]3 99[deg]40
7[min] [min]
May 30-31, 1935.............. 22 MR 3-28A........ Cherry Creek.... CO.............. 39[deg]1 104[deg]3
3[min] 2[min]
May 31, 1935................. 23 GM 5-20......... Woodward........ TX.............. 29[deg]2 99[deg]28
0[min] [min]
July 6-10, 1935.............. 24 NA 1-27......... Hector.......... NY.............. 42[deg]3 76[deg]53
0[min] [min]
Sept. 2-6, 1935.............. 25 SA 1-26......... Easton.......... MD.............. 38[deg]4 76[deg]01
6[min] [min]
Sept. 14-18, 1936............ 26 GM 5-7.......... Broome.......... TX.............. 31[deg]4 100[deg]5
7[min] 0[min]
June 19-20, 1939............. 27 ................ Snyder.......... TX.............. 32[deg]4 100[deg]5
4[min] 5[min]
July 4-5, 1939............... 28 ................ Simpson......... KY.............. 38[deg]1 83[deg]22
3[min] [min]
Aug. 19, 1939................ 29 NA 2-3.......... Manahawkin...... NJ.............. 39[deg]4 74[deg]16
2[min] [min]
June 3-4, 1940............... 30 MR 4-5.......... Grant Township.. NB.............. 42[deg]0 96[deg]53
1[min] [min]
Aug. 6-9, 1940............... 31 LMV 4-24........ Miller Isl...... LA.............. 29[deg]4 92[deg]10
5[min] [min]
Aug. 10-17, 1940............. 32 SA 5-19A........ Keysville....... VA.............. 37[deg]0 78[deg]30
3[min] [min]
Sept. 1, 1940................ 33 NA 2-4.......... Ewan............ NJ.............. 39[deg]4 75[deg]12
2[min] [min]
Sept. 2-6, 1940.............. 34 SW 2-18......... Hallet.......... OK.............. 36[deg]1 96[deg]36
5[min] [min]
Aug. 28-31, 1941............. 35 UMV 1-22........ Haywood......... WI.............. 46[deg]0 91[deg]28
0[min] [min]
Oct. 17-22, 1941............. 36 SA 5-6.......... Trenton......... FL.............. 29[deg]4 82[deg]57
8[min] [min]
July 17-18, 1942............. 37 OR 9-23......... Smethport....... PA.............. 41[deg]5 78[deg]25
0[min] [min]
Oct. 11-17, 1942............. 38 SA 1-28A........ Big Meadows..... VA.............. 38[deg]3 78[deg]26
1[min] [min]
May 6-12, 1943............... 39 SW 2-20......... Warner.......... OK.............. 35[deg]2 95[deg]18
9[min] [min]
May 12-20, 1943.............. 40 SW 2-21......... Nr. Mounds...... OK.............. 35[deg]5 96[deg]04
2[min] [min]
July 27-29, 1943............. 41 GM 5-21......... Devers.......... TX.............. 30[deg]0 94[deg]35
2[min] [min]
Aug. 4-5, 1943............... 42 OR 3-30......... Nr. Glenville... WV.............. 38[deg]5 80[deg]50
6[min] [min]
June 10-13, 1944............. 43 MR 6-15......... Nr. Stanton..... NB.............. 41[deg]5 97[deg]03
2[min] [min]
Aug. 12-15, 1946............. 44 MR 7-2A......... Cole Camp....... MO.............. 38[deg]4 93[deg]13
0[min] [min]
Aug. 12-16, 1946............. 45 MR 7-2B......... Nr. Collinsville IL.............. 38[deg]4 89[deg]59
0[min] [min]
Sept. 26-27, 1946............ 46 GM 5-24......... Nr. San Antonio. TX.............. 29[deg]2 98[deg]29
0[min] [min]
June 23-24, 1948............. 47 ................ Nr. Del Rio..... TX.............. 29[deg]2 100[deg]3
2[min] 7[min]
Sept. 3-7, 1950.............. 48 SA 5-8.......... Yankeetown...... FL.............. 29[deg]0 82[deg]42
3[min] [min]
June 23-28, 1954............. 49 SW 3-22......... Vic Pierce...... TX.............. 30[deg]2 101[deg]2
2[min] 3[min]
Aug. 17-20, 1955............. 50 NA 2-22A........ Westfield....... MA.............. 42[deg]0 72[deg]45
7[min] [min]
May 15-16, 1957.............. 51 ................ Hennessey....... OK.............. 36[deg]0 97[deg]56
2[min] [min]
June 14-15, 1957............. 52 ................ Nr. E. St. Louis IL.............. 38[deg]3 90[deg]24
7[min] [min]
June 23-24, 1963............. 53 ................ David City...... NB.............. 41[deg]1 97[deg]05
4[min] [min]
June 13-20, 1965............. 54 ................ Holly........... CO.............. 37[deg]4 102[deg]2
3[min] 3[min]
June 24, 1966................ 55 ................ Glenullin....... ND.............. 47[deg]2 101[deg]1
1[min] 9[min]
Aug. 12-13, 1966............. 56 ................ Nr. Greely...... NB.............. 41[deg]3 98[deg]32
3[min] [min]
Sept. 19-24, 1967............ 57 SW 3-24......... Falfurrias...... TX.............. 27[deg]1 98[deg]12
6[min] [min]
July 16-17, 1968............. 58 ................ Waterloo........ IA.............. 42[deg]3 92[deg]19
0[min] [min]
July 4-5, 1969............... 59 ................ Nr. Wooster..... OH.............. 40[deg]5 82[deg]00
0[min] [min]
Aug. 19-20, 1969............. 60 NA 2-3.......... Nr. Tyro........ VA.............. 37[deg]4 79[deg]00
9[min] [min]
June 9, 1972................. 61 ................ Rapid City...... SD.............. 44[deg]1 103[deg]3
2[min] 1[min]
June 19-23, 1972............. 62 ................ Zerbe........... PA.............. 40[deg]3 76[deg]31
7[min] [min]
July 21-22, 1972............. 63 ................ Nr. Cushing..... MN.............. 46[deg]1 94[deg]30
0[min] [min]
Sept. 10-12, 1972............ 64 ................ Harlan.......... IA.............. 41[deg]4 95[deg]15
3[min] [min]
Oct. 10-11, 1973............. 65 ................ Enid............ OK.............. 36[deg]2 97[deg]52
5[min] [min]
----------------------------------------------------------------------------------------------------------------
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Table 2--Storms With Rainfall =50% of PMP, U.S. West of Continental Divide (for 10 mi \2\ 6 Hours or
1,000 mi\2\ for One Duration Between 6 and 72 Hours)
----------------------------------------------------------------------------------------------------------------
Storm center Duration
Index ----------------------------------------- for
Storm date No. Latitude Longitude 1,000
Town State mi\2\
----------------------------------------------------------------------------------------------------------------
Aug. 11, 1890................... 1 Palmetto........... NV................ 37[deg]2 117[deg]4 ........
7[min] 2[min]
Aug. 12, 1891................... 2 Campo.............. CA................ 32[deg]3 116[deg]2 ........
6[min] 8[min]
Aug. 28, 1898................... 3 Ft. Mohave......... AZ................ 35[deg]0 114[deg]3 ........
3[min] 6[min]
Oct. 4-6, 1911.................. 4 Gladstone.......... CO................ 37[deg]5 107[deg]3 ........
3[min] 9[min]
Dec. 29, 1913-Jan. 3, 1914...... 5 ................... CA................ 39[deg]5 121[deg]2 ........
5[min] 5[min]
Feb. 17-22, 1914................ 6 Colby Ranch........ CA................ 34[deg]1 118[deg]0 ........
8[min] 7[min]
Feb. 20-25, 1917................ 7 ................... CA................ 37[deg]3 119[deg]3 ........
5[min] 6[min]
Sept. 13, 1918.................. 8 Red Bluff.......... CA................ 40[deg]1 122[deg]1 ........
0[min] 4[min]
Feb. 26-Mar 4, 1938............. 9 ................... CA................ 34[deg]1 117[deg]1 ........
4[min] 1[min]
Mar. 30-Apr. 2, 1931............ 10 ................... ID................ 46[deg]3 114[deg]5 24
0[min] 0[min]
Feb. 26, 1932................... 11 Big Four........... WA................ 48[deg]0 121[deg]3 ........
5[min] 0[min]
Nov. 21, 1933................... 12 Tatoosh Is......... WA................ 48[deg]2 124[deg]4 ........
3[min] 4[min]
Jan. 20-25, 1935................ 13 ................... WA................ 47[deg]3 123[deg]3 6
0[min] 0[min]
Jan. 20-25, 1935................ 14 ................... WA................ 47[deg]0 122[deg]0 72
0[min] 0[min]
Feb. 4-8, 1937.................. 15 Cyamaca Dam........ CA................ 33[deg]0 116[deg]3 ........
0[min] 5[min]
Dec. 9-12, 1937................. 16 ................... CA................ 38[deg]5 122[deg]4 ........
1[min] 3[min]
Feb. 27-Mar. 4, 1938............ 17 ................... AZ................ 34[deg]5 111[deg]4 12
7[min] 4[min]
Jan. 19-24, 1943................ 18 ................... CA................ 37[deg]3 119[deg]2 18
5[min] 5[min]
Jan. 19-24, 1943................ 19 Hoegee's Camp...... CA................ 34[deg]1 118[deg]0 ........
3[min] 2[min]
Jan. 30-Feb. 3, 1945............ 20 ................... CA................ 37[deg]3 119[deg]3 ........
5[min] 0[min]
Dec. 27, 1945................... 21 Mt. Tamalpias...... CA................ 37[deg]5 122[deg]3 ........
4[min] 4[min]
Nov. 13-21, 1950................ 22 ................... CA................ 36[deg]3 118[deg]3 24
0[min] 0[min]
Aug. 25-30, 1951................ 23 ................... AZ................ 34[deg]0 112[deg]2 72
7[min] 1[min]
July 19, 1955................... 24 Chiatovich Flat.... CA................ 37[deg]4 118[deg]1 ........
4[min] 5[min]
Aug. 16, 1958................... 25 Morgan............. UT................ 41[deg]0 111[deg]3 ........
3[min] 8[min]
Sept. 18, 1959.................. 26 Newton............. CA................ 40[deg]2 122[deg]1 ........
2[min] 2[min]
June 7-8, 1964.................. 27 Nyack Ck........... MT................ 48[deg]3 113[deg]3 12
0[min] 8[min]
Sept. 3-7, 1970................. 28 ................... UT................ 37[deg]3 109[deg]0 6
8[min] 4[min]
Sept. 3-7, 1970................. 29 ................... AZ................ 33[deg]4 110[deg]5 6
9[min] 6[min]
June 7, 1972.................... 30 Bakersfield........ CA................ 35[deg]2 119[deg]0 ........
5[min] 3[min]
Dec. 9-12, 1937................. 31 ................... CA................ 39[deg]4 121[deg]3 48
5[min] 0[min]
----------------------------------------------------------------------------------------------------------------
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Appendix D to Sec. 222.6--Recommended Guidelines for Safety Inspection
of Dams
Department of the Army--Office of the Chief of Engineers
Preface
The recommended guidelines for the safety inspection of dams were
prepared to outline principal factors to be weighed in the determination
of existing or potential hazards and to define the scope of activities
to be undertaken in the safety inspection of dams. The establishment of
rigid criteria or standards is not intended. Safety must be evaluated in
the light of peculiarities and local conditions at a particular dam and
in recognition of the many factors involved, some of which may not be
precisely known. This can only be done by competent, experienced
engineering judgment, which the guidelines are intended to supplement
and not supplant. The guidelines are intended to be flexible, and the
proper flexibility must be achieved through the employment of
experienced engineering personnel.
Conditions found during the investigation which do not meet
guideline recommendations should be assessed by the investigator as to
their import from the standpoint of the involved degree of risk. Many
deviations will not compromise project safety and the investigator is
expected to identify them in this manner if that is the case. Others
will involve various degrees of risk, the proper evaluation of which
will afford a basis for priority of subsequent attention and possible
remedial action.
The guidelines present procedures for investigating and evaluating
existing conditions for the purpose of identifying deficiencies and
hazardous conditions. The two phases of investigation outlined in the
guidelines are expected to accomplish only this and do not encompass in
scope the engineering which will be required to perform the design
studies for corrective modification work.
It is recognized that some States may have established or will adopt
inspection criteria incongruous in some respects with these guidelines.
In such instances assessments of project safety should recognize the
State's requirements as well as guideline recommendations.
The guidelines were developed with the help of several Federal
agencies and many State agencies, professional engineering
organizations, and private engineers. In reviewing two drafts of the
guidelines they have contributed many helpful suggestions. Their
contributions are deeply appreciated and have made it possible to evolve
a document representing a consensus of the engineering fraternity. As
experience is gained with use of the guidelines, suggestions for future
revisions will be generated. All such suggestions should be directed to
the Chief of Engineers, U.S. Army, DAEN-CWE-D, Washington, D.C. 20314.
Recommended Guidelines for Safety Inspection of Dams
Table of Contents
Preface
Chapter 1--Introduction
Para.
1.1 Purpose.
1.2 Applicability.
1.3 Authority.
Chapter 2--General Requirements
2.1 Classification of dams.
2.1.1 Size.
2.1.2 Hazard potential.
2.2 Selection of dams to be investigated.
2.3 Technical investigations.
2.4 Qualifications of investigators.
2.5 Reports.
Chapter 3--Phase I Investigation
3.1 Purpose.
3.2 Scope.
3.3 Engineering data.
3.4 Field inspections.
3.5 Evaluation of hydraulic and hydrologic features.
3.5.1 Design data.
3.5.2 Experience data.
3.6 Evaluation of structural stability.
3.6.1 Design and construction data.
3.6.2 Operating records.
3.6.3 Post contruction changes.
3.6.4 Seismic stability.
Chapter 4--Phase II Investigation
4.1 Purpose.
4.2 Scope.
4.3 Hydraulic and hydrologic analysis.
4.3.1 Maximum water surface based on SDF peak inflow.
4.3.1.1 Peak for 100-year flood.
4.3.1.2 Peak for PMF or fraction thereof.
4.3.2 Maximum water surface based on SDF hydrograph.
4.3.3 Acceptable procedures.
4.3.4 Freeboard allowances.
4.4 Stability investigations.
4.4.1 Foundation and material investigations.
4.4.2 Stability assessment.
4.4.2.1 Seismic stability.
4.4.2.2 Clay shale foundation.
4.4.3 Embankment dams.
4.4.3.1 Liquefaction.
4.4.3.2 Shear failure.
4.4.3.3 Loading conditions.
4.4.3.4 Safety factors.
4.4.3.5 Seepage failure.
4.4.3.6 Seepage analyses.
[[Page 286]]
4.4.4 Concrete dams and appurtenant structures.
4.4.4.1 Requirements for stability.
4.4.4.2 Loads.
4.4.4.3 Stresses.
4.4.4.4 Overturning.
4.4.4.5 Sliding.
4.4.4.5.1 Sliding resistance.
4.4.4.5.2 Downstream resistance.
4.4.4.5.3 Safety factor.
Chapter 5--Reports
5.1 General.
5.2 Preparation of report.
5.2.1 Phase I reports.
5.2.2 Phase II reports.
Tables
Table
1 Size classification.
2 Hazard potential classification.
3 Hydrologic evaluation guidelines.
4 Factors of safety (embankment dams).
Figures
Fig.
1 Seismic zone map of contiguous States.
2 Seismic zone map of California, Nevada and Arizona.
3 Seismic zone map of Alaska.
4 Seismic zone map of Hawaii.
5 Design envelope for Case I (Table 4).
6 Design envelope for Cases II and III (Table 4).
Appendixes
Appendix I to App. D--Engineering data
Appendix II to App. D--Inspection items
Appendix III to App. D--Pub. L. 92-367
Chapter 1--Introduction
1.1. Purpose. This document provides recommended guidelines for the
inspection and evaluation of dams to determine if they constitute
hazards to human life or property.
1.2. Applicability. The procedures and guidelines outlined in this
document apply to the inspection and evaluation of all dams as defined
in the National Dam Inspection Act, Public Law 92-367. Included in this
program are all artificial barriers together with appurtenant works
which impound or divert water and which (1) are twenty-five feet or more
in height or (2) have an impounding capacity of fifty acre-feet or more.
Not included are barriers which are six feet or less in height,
regardless of storage capacity, or barriers which have a storage
capacity at maximum water storage elevation of fifteen acre-feet or less
regardless of height.
1.3. Authority. The Dam Inspection Act, Public Law 92-367 (Appendix
III), authorized the Secretary of the Army, through the Corps of
Engineers, to initiate a program of safety inspection of dams throughout
the United States. The Chief of Engineers issues these guidelines
pursuant to that authority.
Chapter 2--General Requirements
2.1. Classification of dams. Dams should be classified in accordance
with size and hazard potential in order to formulate a priority basis
for selecting dams to be included in the inspection program and also to
provide compatibility between guideline requirements and involved risks.
When possible the initial classifications should be based upon
information listed in the National Inventory of Dams with respect to
size, impoundment capacity and hazard potential. It may be necessary to
reclassify dams when additional information becomes available.
2.1.1. Size. The classification for size based on the height of the
dam and storage capacity should be in accordance with Table 1. The
height of the dam is established with respect to the maximum storage
potential measured from the natural bed of the stream or watercourse at
the downstream toe of the barrier, or if it is not across a stream or
watercourse, the height from the lowest elevation of the outside limit
of the barrier, to the maximum water storage elevation. For the purpose
of determining project size, the maximum storage elevation may be
considered equal to the top of dam elevation. Size classification may be
determined by either storage or height, whichever gives the larger size
category.
Table 1--Size Classification
------------------------------------------------------------------------
Impoundment
Category ---------------------------------------
Storage (ac-ft) Height (ft)
------------------------------------------------------------------------
Small........................... <1,000 and =50. eq>=25.
Intermediate.................... =1,000 =40 and
and <50,000. <100.
Large........................... =50,000 =100.
------------------------------------------------------------------------
2.1.2. Hazard Potential. The classification for potential hazards
should be in accordance with Table 2. The hazards pertain to potential
loss of human life or property damage in the area downstream of the dam
in event of failure or misoperation of the dam or appurtenant
facilities. Dams conforming to criteria for the low hazard potential
category generally will be located in rural or agricultural areas where
failure may damage farm buildings, limited agricultural land, or
township and country roads. Significant hazard potential category
structures will be those located in predominantly rural or agricultural
areas where failure may damage isolated homes, secondary highways or
minor railroads or cause interruption of use or service of relatively
important public utilities. Dams in the high hazard potential category
will be those located where failure may cause serious damage to homes,
extensive agricultural, industrial and commercial facilities, important
public utilities, main highways, or railroads.
[[Page 287]]
Table 2--Hazard Potential Classification
----------------------------------------------------------------------------------------------------------------
Loss of life (extent of Economic loss (extent of
Category development) development)
----------------------------------------------------------------------------------------------------------------
Low.................................... None expected (No permanent Minimal (Undeveloped to occasional
structures for human habitation). structures or agriculture).
Significant............................ Few (No urban developments and no Appreciable (Notable agriculture,
more than a small number of industry or structures).
inhabitable structures).
High................................... More than few...................... Excessive (Extensive community,
industry or agriculture).
----------------------------------------------------------------------------------------------------------------
2.2. Selection of dams to be investigated. The selection of dams to
be investigated should be based upon an assessment of existing
developments in flood hazard areas. Those dams possessing a hazard
potential classified high or significant as indicated in Table 2 should
be given first and second priorities, respectively, in the inspection
program. Inspection priorities within each category may be developed
from a consideration of factors such as size classification and age of
the dam, the population size in the downstream flood area, and potential
developments anticipated in flood hazard areas.
2.3. Technical Investigations. A detailed, systematic, technical
inspection and evaluation should be made of each dam selected for
investigation in which the hydraulic and hydrologic capabilities,
structural stability and operational adequacy of project features are
analyzed and evaluated to determine if the dam constitutes a danger to
human life or property. The investigation should vary in scope and
completeness depending upon the availability and suitability of
engineering data, the validity of design assumptions and analyses and
the condition of the dam. The minimum investigation will be designated
Phase I, and an in-depth investigation designated Phase II should be
made where deemed necessary. Phase I investigations should consist of a
visual inspection of the dam, abutments and critical appurtenant
structures, and a review of readily available engineering data. It is
not intended to perform costly explorations or analyses during Phase I.
Phase II investigations should consist of all additional engineering
investigations and analyses found necessary by results of the Phase I
investigation.
2.4. Qualifications of investigators. The technical investigations
should be conducted under the direction of licensed professional
engineers experienced in the investigation, design, construction and
operation of dams, applying the disciplines of hydrologic, hydraulic,
soils and structural engineering and engineering geology. All field
inspections should be conducted by qualified engineers, engineering
geologists and other specialists, including experts on mechanical and
electrical operation of gates and controls, knowledgeable in the
investigation, design, construction and operation of dams.
Chapter 3--Phase I Investigation
3.1. Purpose. The primary purpose of the Phase I investigation
program is to identify expeditiously those dams which may pose hazards
to human life or property.
3.2. Scope. The Phase I investigation will develop an assessment of
the general condition with respect to safety of the project based upon
available data and a visual inspection, determine any need for emergency
measures and conclude if additional studies, investigation and analyses
are necessary and warranted. A review will be made of pertinent existing
and available engineering data relative to the design, construction and
operation of the dam and appurtenant structures, including electrical
and mechanical operating equipment and measurements from inspection and
performance instruments and devices; and a detailed systematic visual
inspection will be performed of those features relating to the stability
and operational adequacy of the project. Based upon findings of the
review of engineering data and the visual inspection, an evaluation will
be made of the general condition of the dam, including where possible
the assessment of the hydraulic and hydrologic capabilities and the
structural stability.
3.3. Engineering data. To the extent feasible the engineering data
listed in Appendix I relating to the design, construction and operation
of the dam and appurtenant structures, should be collected from existing
records and reviewed to aid in evaluating the adequacy of hydraulic and
hydrologic capabilities and stability of the dam. Where the necessary
engineering data are unavailable, inadequate or invalid, a listing
should be made of those specific additional data deemed necessary by the
engineer in charge of the investigation and included in the Phase I
report.
3.4. Field inspections. The field inspection of the dam, appurtenant
stuctures, reservoir area, and downstream channel in the vicinity of the
dam should be conducted in a systematic manner to minimize the
possibility of any significant feature being overlooked. A detailed
checklist should be developed and followed for each dam inspected to
document
[[Page 288]]
the examination of each significant structural and hydraulic feature
including electrical and mechanical equipment for operation of the
control facilities that affect the safety of the dam.
3.4.1. Particular attention should be given to detecting evidence of
leakage, erosion, seepage, slope instability, undue settlement,
displacement, tilting, cracking, deterioration, and improper functioning
of drains and relief wells. The adequacy and quality of maintenance and
operating procedures as they pertain to the safety of the dam and
operation of the control facilities should also be assessed.
3.4.2. Photographs and drawings should be used freely to record
conditions in order to minimize descriptions.
3.4.3. The field inspection should include appropriate features and
items, including but not limited to those listed in Appendix II, which
may influence the safety of the dam or indicate potential hazards to
human life or property.
3.5. Evaluation of hydraulic and hydrologic Features.
3.5.1. Design data. Original hydraulic and hydrologic design
assumptions obtained from the project records should be assessed to
determine their acceptability in evaluating the safety of the dam. All
constraints on water control such as blocked entrances, restrictions on
operation of spillway and outlet gates, inadequate energy dissipators or
restrictive channel conditions, significant reduction in reservoir
capacity by sediment deposits and other factors should be considered in
evaluating the validity of discharge ratings, storage capacity,
hydrographs, routings and regulation plans. The discharge capacity and/
or storage capacity should be capable of safely handling the recommended
spillway design flood for the size and hazard potential classification
of the dam as indicated in Table 3. The hydraulic and hydrologic
determinations for design as obtained from project records will be
acceptable if conventional techniques similar to the procedures outlined
in paragraph 4.3. were used in obtaining the data. When the project
design flood actually used exceeds the recommended spillway design
flood, from Table 3, the project design flood will be acceptable in
evaluating the safety of the dam.
Table 3--Hydrologic Evaluation Guidelines
[Recommended spillway design floods]
------------------------------------------------------------------------
Spillway design
Hazard Size flood (SDF) \1\
------------------------------------------------------------------------
Low............................. Small............. 50 to 100-yr
frequency.
Intermediate...... 100-yr to \1/2\
PMF.
Large............. \1/2\ PMF to PMF.
Significant..................... Small............. 100-yr to \1/2\
PMF.
Intermediate...... \1/2\ PMF to PMF.
Large............. PMF.
High............................ Small............. \1/2\ PMF to PMF.
Intermediate...... PMF.
Large............. PMF.
------------------------------------------------------------------------
\1\ The recommended design floods in this column represent the magnitude
of the spillway design flood (SDF), which is intended to represent the
largest flood that need be considered in the evaluation of a given
project, regardless of whether a spillway is provided; i.e., a given
project should be capable of safely passing the appropriate SDF. Where
a range of SDF is indicated, the magnitude that most closely relates
to the involved risk should be selected.
1000-yr=100-Year Exceedence Interval. The flood magnitude expected to be
exceeded, on the average, of once in 100 years. It may also be expressed
as an exceedence frequency with a one-percent chance of being exceeded
in any given year.
PMF=Probable Maximum Flood. The flood that may be expected from the most
severe combination of critical meteorologic and hydrologic conditions
that are reasonably possible in the region. The PMF is derived from
probable maximum precipitation (PMP), which information is generally
available from the National Weather Service, NOAA. Most Federal agencies
apply reduction factors to the PMP when appropriate. Reductions may be
applied because rainfall isohyetals are unlikely to conform to the exact
shape of the drainage basin and/or the storm is not likely to center
exactly over the drainage basin. In some cases local topography will
cause changes from the generalized PMP values, therefore it may be
advisable to contact Federal construction agencies to obtain the
prevailing practice in specific areas.
3.5.2. Experience data. In some cases where design data are lacking,
an evaluation of overtopping potential may be based on watershed
characteristics and rainfall and reservoir records. An estimate of the
probable maximum flood may also be developed from a conservative,
generalized comparison of the drainage area size and the magnitude of
recently adopted probable maximum floods for damsites in comparable
hydrologic regions. Where the review of such experience data indicates
that the recommended spillway design flood would not cause overtopping
additional hydraulic and hydrologic determinations will be unnecessary.
3.6. Evaluation of structural stability. The Phase I evaluations of
structural adequacy of project features are expected to be based
principally on existing conditions as revealed by the visual inspection,
together with available design and construction information and records
of performance. The objectives are to determine the existence of
conditions which are hazardous, or which with time might develop into
safety hazards,
[[Page 289]]
and to formulate recommendations pertaining to the need for any
additional studies, investigations, or analyses. The results of this
phase of the inspection must rely very substantially upon the experience
and judgment of the inspecting engineer.
3.6.1. Design and construction data. The principal design
assumptions and analyses obtained from the project records should be
assessed. Original design and construction records should be used
judiciously, recognizing the restricted applicability of such data as
material strengths and permeabilities, geological factors and
construction descriptions. Original stability studies and analyses
should be acceptable if conventional techniques and procedures similar
to those outlined in paragraph 4.4 were employed, provided that review
of operational and performance data confirm that the original design
assumptions were adequately conservative. The need for such analyses
where either none exist or the originals are incomplete or
unsatisfactory will be determined by the inspecting engineer based upon
other factors such as condition of structures, prior maximum loadings
and the hazard degree of the project. Design assumptions and analyses
should include all applicable loads including earthquake and indicate
the structure's capability to resist overturning, sliding and
overstressing with adequate factors of safety. In general seepage and
stability analyses comparable to the requirements of paragraph 4.4
should be on record for all dams in the high hazard category and large
dams in the significant hazard category. This requirement for other dams
will be subject to the opinion of the inspecting engineer.
3.6.2. Operating records. The performance of structures under prior
maximum loading conditions should in some instances provide partial
basis for stability evaluation. Satisfactory experience under loading
conditions not expected to be exceeded in the future should generally be
indicative of satisfactory stability, provided adverse changes in
physical conditions have not occurred. Instrumentation observations of
forces, pressures, loads, stresses, strains, displacements, deflections
or other related conditions should also be utilized in the safety
evaluation. Where such data indicate abnormal behavior, unsafe movement
or deflections, or loadings which adversely affect the stability or
functioning of the structure, prompt reporting of such circumstances is
required without the delay for preparation of the official inspection
report.
3.6.3. Post construction changes. Data should be collected on
changes which have occurred since project construction that might
influence the safety of the dam such as road cuts, quarries, mining and
groundwater changes.
3.6.4. Seismic stability. An assessment should be made of the
potential vulnerability of the dam to seismic events and a
recommendation developed with regard to the need for additional seismic
investigation. In general, projects located in Seismic Zones 0, 1 and 2
may be assumed to present no hazard from earthquake provided static
stability conditions are satisfactory and conventional safety margins
exist. Dams in Zones 3 and 4 should, as a minimum, have on record
suitable analyses made by conventional equivalent static load methods.
The seismic zones together with appropriate coefficients for use in such
analyses are shown in Figures 1 through 4. Boundary lines are
approximate and in the event of doubt about the proper zone, the higher
zone should be used. All high hazard category dams in Zone 4 and high
hazard dams of the hydraulic fill type in Zone 3 should have a stability
assessment based upon knowledge of regional and local geology,
engineering seismology, in situ properties of materials and appropriate
dynamic analytical and testing procedures. The assessment should include
the possibility of physical displacement of the structures due to
movements along active faults. Departure from this general guidance
should be made whenever in the judgment of the investigating engineer
different seismic stability requirements are warranted because of local
geological conditions or other reasons.
Chapter 4--Phase II Investigation
4.1. Purpose. The Phase II investigation will be supplementary to
Phase I and should be conducted when the results of the Phase I
investigation indicate the need for additional in-depth studies,
investigations or analyses.
4.2. Scope. The Phase II investigation should include all additional
studies, investigations and analyses necessary to evaluate the safety of
the dam. Included, as required, will be additional visual inspections,
measurements, foundation exploration and testing, materials testing,
hydraulic and hydrologic analysis and structural stability analyses.
4.3. Hydraulic and hydrologic analysis. Hydraulic and hydrologic
capabilities should be determined using the following criteria and
procedures. Depending on the project characteristics, either the
spillway design flood peak inflow or the spillway design flood
hydrograph should be the basis for determining the maximum water surface
elevation and maximum outflow. If the operation or failure of upstream
water control projects would have significant impact on peak flow or
hydrograph analyses, the impact should be assessed.
4.3.1. Maximum water surface based on SDF peak inflow. When the
total project discharge capability at maximum pool exceeds the peak
inflow of the recommended SDF, and
[[Page 290]]
operational constraints would not prevent such a release at controlled
projects, a reservoir routing is not required. The maximum discharge
should be assumed equal to the peak inflow of the spillway design flood.
Flood volume is not controlling in this situation and surcharge storage
is either absent or is significant only to the extent that it provides
the head necessary to develop the release capability required.
4.3.1.1. Peak for 100-year flood. When the 100-year flood is
applicable under the provisions of Table 3 and data are available, the
spillway design flood peak inflow may be determined by use of ``A
Uniform Technique for Determining Flood Frequencies,'' Water Resources
Council (WRC), Hydrology Committee, Bulletin 15, December 1967. Flow
frequency information from regional analysis is generally preferred over
single station results when available and appropriate. Rainfall-runoff
techniques may be necessary when there are inadequate runoff data
available to make a reasonable estimate of flow frequency.
4.3.1.2. Peak for PMF or fraction thereof. When either the Probable
Maximum Flood peak or a fraction thereof is applicable under the
provisions of Table 3, the unit hydrograph--infiltration loss technique
is generally the most expeditious method of computing the spillway
design flood peak for most projects. This technique is discussed in the
following paragraph.
4.3.2. Maximum water surface based on SDF hydrograph. Both peak and
volume are required in this analysis. Where surcharge storage is
significant, or where there is insufficient discharge capability at
maximum pool to pass the peak inflow of the SDF, considering all
possible operational constraints, a flood hydrograph is required. When
there are upstream hazard areas that would be imperiled by fast rising
reservoirs levels, SDF hydrographs should be routed to ascertain
available time for warning and escape. Determination of probable maximum
precipitation or 100-year precipitation, which ever is applicable, and
unit hydrographs or runoff models will be required, followed by the
determination of the PMF or 100-year flood. Conservative loss rates
(significantly reduced by antecedent rainfall conditions where
appropriate) should be estimated for computing the rainfall excess to be
utilized with unit hydrographs. Rainfall values are usually arranged
with gradually ascending and descending rates with the maximum rate late
in the storm. When applicable, conservatively high snowmelt runoff rates
and appropriate releases from upstream projects should be assumed. The
PMP may be obtained from National Weather Service (NWS) publications
such as Hydrometeorological Report (HMR) 33. Special NWS publications
for particular areas should be used when available. Rainfall for the
100-year frequency flood can be obtained from the NWS publication
``Rainfall Frequency Atlas of the United States,'' Technical Paper No.
40; Atlas 2, ``Precipitation Frequency Atlas of Western United States;''
or other NWS publications. The maximum water surface elevation and
spillway design flood outflow are then determined by routing the inflow
hydrograph through the reservoir surcharge storage, assuming a starting
water surface at the bottom of surcharge storage, or lower when
appropriate. For projects where the bottom of surcharge space is not
distinct, or the flood control storage space (exclusive of surcharge) is
appreciable, it may be appropriate to select starting water surface
elevations below the top of the flood control storage for routings.
Conservatively high starting levels should be estimated on the basis of
hydrometeorological conditions reasonably characteristic for the region
and flood release capability of the project. Necessary adjustment of
reservoir storage capacity due to existing or future sediment or other
encroachment may be approximated when accurate determination of
deposition is not practicable.
4.3.3. Acceptable procedures. Techniques for performing hydraulic
and hydrologic analyses are generally available from publications
prepared by Federal agencies involved in water resources development or
textbooks written by the academic community. Some of these procedures
are rather sophisticated and require expensive computational equipment
and large data banks. While results of such procedures are generally
more reliable than simplified methods, their use is generally not
warranted in studies connected with this program unless they can be
performed quickly and inexpensively. There may be situations where the
more complex techniques have to be employed to obtain reliable results;
however, these cases will be exceptions rather than the rule. Whenever
the acceptability of procedures is in question, the advice of competent
experts should be sought. Such expertise is generally available in the
Corps of Engineers, Bureau of Reclamation and Soil Conservation Service.
Many other agencies, educational facilities and private consultants can
also provide expert advice. Regardless of where such expertise is based,
the qualification of those individuals offering to provide it should be
carefully examined and evaluated.
4.3.4. Freeboard allowances. Guidelines on specific minimum
freeboard allowances are not considered appropriate because of the many
factors involved in such determinations. The investigator will have to
assess the critical parameters for each project and develop its minimum
requirement. Many projects are reasonably safe without freeboard
allowance because they are designed for overtopping, or other factors
minimize possible overtopping. Conversely,
[[Page 291]]
freeboard allowances of several feet may be necessary to provide a safe
condition. Parameters that should be considered include the duration of
high water levels in the reservoir during the design flood; the
effective wind fetch and reservoir depth available to support wave
generation; the probability of high wind speed occurring from a critical
direction; the potential wave runup on the dam based on roughness and
slope; and the ability of the dam to resist erosion from overtopping
waves.
4.4 Stability investigations. The Phase II stability investigations
should be compatible with the guidelines of this paragraph.
4.4.1 Foundation and material investigations. The scope of the
foundation and materials investigation should be limited to obtaining
the information required to analyze the structural stability and to
investigate any suspected condition which would adversely affect the
safety of the dam. Such investigations may include borings to obtain
concrete, embankment, soil foundation, and bedrock samples; testing
specimens from these samples to determine the strength and elastic
parameters of the materials, including the soft seams, joints, fault
gouge and expansive clays or other critical materials in the foundation;
determining the character of the bedrock including joints, bedding
planes, fractures, faults, voids and caverns, and other geological
irregularities; and installing instruments for determining movements,
strains, suspected excessive internal seepage pressures, seepage
gradients and uplift forces. Special investigations may be necessary
where suspect rock types such as limestone, gypsum, salt, basalt,
claystone, shales or others are involved in foundations or abutments in
order to determine the extent of cavities, piping or other deficiencies
in the rock foundation. A concrete core drilling program should be
undertaken only when the existence of significant structural cracks is
suspected or the general qualitative condition of the concrete is in
doubt. The tests of materials will be necessary only where such data are
lacking or are outdated.
4.4.2. Stability assessment. Stability assessments should utilize in
situ properties of the structure and its foundation and pertinent
geologic information. Geologic information that should be considered
includes groundwater and seepage conditions; lithology, stratigraphy,
and geologic details disclosed by borings, ``as-built'' records, and
geologic interpretation; maximum past overburden at site as deduced from
geologic evidence; bedding, folding and faulting; joints and joint
systems; weathering; slickensides, and field evidence relating to
slides, faults, movements and earthquake activity. Foundations may
present problems where they contain adversely oriented joints,
slickensides or fissured material, faults, seams of soft materials, or
weak layers. Such defects and excess pore water pressures may contribute
to instability. Special tests may be necessary to determine physical
properties of particular materials. The results of stability analyses
afford a means of evaluating the structure's existing resistance to
failure and also the effects of any proposed modifications. Results of
stability analyses should be reviewed for compatibility with performance
experience when possible.
4.4.2.1. Seismic stability. The inertial forces for use in the
conventional equivalent static force method of analysis should be
obtained by multiplying the weight by the seismic coefficient and should
be applied as a horizontal force at the center of gravity of the section
or element. The seismic coefficients suggested for use with such
analyses are listed in Figures 1 through 4. Seismic stability
investigations for all high hazard category dams located in Seismic Zone
4 and high hazard dams of the hydraulic fill type in Zone 3 should
include suitable dynamic procedures and analyses. Dynamic analyses for
other dams and higher seismic coefficients are appropriate if in the
judgment of the investigating engineer they are warranted because of
proximity to active faults or other reasons. Seismic stability
investigations should utilize ``state-of-the-art'' procedures involving
seismological and geological studies to establish earthquake parameters
for use in dynamic stability analyses and, where appropriate, the
dynamic testing of materials. Stability analyses may be based upon
either time-history or response spectra techniques. The results of
dynamic analyses should be assessed on the basis of whether or not the
dam would have sufficient residual integrity to retain the reservoir
during and after the greatest or most adverse earthquake which might
occur near the project location.
4.4.2.2. Clay shale foundation. Clay shale is a highly
overconsolidated sedimentary rock comprised predominantly of clay
minerals, with little or no cementation. Foundations of clay shales
require special measures in stability investigations. Clay shales,
particularly those containing montmorillonite, may be highly susceptible
to expansion and consequent loss of strength upon unloading. The shear
strength and the resistance to deformation of clay shales may be quite
low and high pore water pressures may develop under increase in load.
The presence of slickensides in clay shales is usually an indication of
low shear strength. Prediction of field behavior of clay shales should
not be based solely on results of conventional laboratory tests since
they may be misleading. The use of peak shear strengths for clay shales
in stability analyses may be unconservative because of nonuniform stress
distribution and possible progressive failures. Thus the available shear
resistance may be less than if the peak shear strength
[[Page 292]]
were mobilized simultaneously along the entire failure surface. In such
cases, either greater safety factors or residual shear strength should
be used.
4.4.3. Embankment dams.
4.4.3.1. Liquefaction. The phenomenon of liquefaction of loose,
saturated sands and silts may occur when such materials are subjected to
shear deformation or earthquake shocks. The possibility of liquefaction
must presently be evaluated on the basis of empirical knowledge
supplemented by special laboratory tests and engineering judgment. The
possiblitity of liquefaction in sands diminishes as the relative density
increases above approximately 70 percent. Hydraulic fill dams in Seismic
Zones 3 and 4 should receive particular attention since such dams are
susceptible to liquefaction under earthquake shocks.
4.4.3.2. Shear failure. Shear failure is one in which a portion of
an embankment or of an embankment and foundation moves by sliding or
rotating relative to the remainder of the mass. It is conventionally
represented as occurring along a surface and is so assumed in stability
analyses, although shearing may occur in a zone of substantial
thickness. The circular arc or the sliding wedge method of analyzing
stability, as pertinent, should be used. The circular arc method is
generally applicable to essentially homogeneous embankments and to soil
foundations consisting of thick deposits of fine-grained soil containing
no layers significantly weaker than other strata in the foundation. The
wedge method is generally applicable to rockfill dams and to earth dams
on foundations containing weak layers. Other methods of analysis such as
those employing complex shear surfaces may be appropriate depending on
the soil and rock in the dam and foundation. Such methods should be in
reputable usage in the engineering profession.
4.4.3.3. Loading conditions. The loading conditions for which the
embankment structures should be investigated are (I) Sudden drawdown
from spillway crest elevation or top of gates, (II) Partial pool, (III)
Steady state seepage from spillway crest elevation or top of gate
elevation, and (IV) Earthquake. Cases I and II apply to upstream slopes
only; slopes; and Case IV applies to both upstream and downstream Case
III applies to downstream slopes. A summary of suggested strengths and
safety factors are shown in Table 4.
Table 4--Factors of Safety\1\
----------------------------------------------------------------------------------------------------------------
Factor
Case and loading condition of Shear \2\ strength Remarks
safety
----------------------------------------------------------------------------------------------------------------
I Sudden drawdown from spillway crest or \3\ 1.2 Minimum composite of R and Within the drawdown zone
top of gates to minimum drawdown S shear strengths. See submerged unit weights of
elevation. Figure 5. materials are used for
computing forces resisting
sliding and saturated unit
weights are used for computing
forces contributing to sliding.
II Partial pool with assumed horizontal 1.5 R+S/2 for RS........ of R and
S shear strengths. See Figure
6.
III Steady seepage from spillway crest 1.5 Same as Case II............
or top of gates with Kh/Kv=9 assumed\4\.
IV Earthquake (Cases II and III with 1.0 (\5\ )..................... See Figures 1 through 4 for
seismic loading). Seismic Coefficients.
----------------------------------------------------------------------------------------------------------------
\1\ Not applicable to embankments on clay shale foundation. Experience has indicated special problems in
determination of design shear strengths for clay shale foundations and acceptable safety factors should be
compatible with the confidence level in shear strength assumptions.
\2\ Other strength assumptions may be used if in common usage in the engineering profession.
\3\ The safety factor should not be less than 1.5 when drawdown rate and pore water pressure developed from flow
nets are used in stability analyses.
\4\ Kh/Kv is the ratio of horizontal to vertical permeability. A minimum of 9 is suggested for use in compacted
embankments and alluvial sediments.
\5\ Use shear strength for case analyzed without earthquake. It is not necessary to analyze sudden drawdown for
earthquake loading. Shear strength tests are classified according to the controlled drainage conditions
maintained during the test. R tests are those in which specimen drainage is allowed during consolidation (or
swelling) under initial stress conditions, but specimen drainage is not allowed during application of shearing
stresses. S tests allow full drainage during initial stress application and shearing is at a slow rate so that
complete specimen drainage is permitted during the complete test.
4.4.3.4. Safety factors. Safety factors for embankment dam stability
studies should be based on the ratio of available shear strength to
developed shear strength, SD :
[GRAPHIC] [TIFF OMITTED] TC15NO91.000
Where:
C=Cohesion
[phis]=Angle of internal friction
[sigma]=Normal stress
The factors of safety listed in Table 4 are recommended as minimum
acceptable. Final accepted factors of safety should depend upon the
degree of confidence the investigating engineer has in the engineering
data
[[Page 293]]
available to him. The consequences of a failure with respect to human
life and property damage are important considerations in establishing
factors of safety for specific investigations.
4.4.3.5. Seepage failure. A critical uncontrolled underseepage or
through seepage condition that develops during a rising pool can quickly
reduce a structure which was stable under previous conditions, to a
total structural failure. The visually confirmed seepage conditions to
be avoided are (1) the exit of the phreatic surface on the downstream
slope of the dam and (2) development of hydrostatic heads sufficient to
create in the area downstream of the dam sand boils that erode materials
by the phenomenon known as ``piping'' and (3) localized concentrations
of seepage along conduits or through pervious zones. The dams most
susceptible to seepage problems are those built of or on pervious
materials of uniform fine particle size, with no provisions for an
internal drainage zone and/or no underseepage controls.
4.4.3.6. Seepage analyses. Review and modifications to original
seepage design analyses should consider conditions observed in the field
inspection and piezometer instrumentation. A seepage analysis should
consider the permeability ratios resulting from natural deposition and
from compaction placement of materials with appropriate variation
between horizontal and vertical permeability. An underseepage analysis
of the embankment should provide a critical gradient factor of safety
for the maximum head condition of not less than 1.5 in the area
downstream of the embankment.
[GRAPHIC] [TIFF OMITTED] TC15NO91.001
Where:
ic=Critical gradient
i=Design gradient
H=Uplift head at downstream toe of dam measured above tailwater
Hc=The critical uplift
Db=The thickness of the top impervious blanket at the
downstream toe of the dam
[gamma]m=The estimated saturated unit weight of the material
in the top impervious blanket
[gamma]w=The unit weight of water
Where a factor of safety less than 1.5 is obtained the provision of
an underseepage control system is indicated. The factor of safety of 1.5
is a recommended minimum and may be adjusted by the responsible engineer
based on the competence of the engineering data.
4.4.4. Concrete dams and appurtenant structures.
4.4.4.1. Requirements for stability. Concrete dams and structures
appurtenant to embankment dams should be capable of resisting
overturning, sliding and overstressing with adequate factors of safety
for normal and maximum loading conditions.
4.4.4.2. Loads. Loadings to be considered in stability analyses
include the water load on the upstream face of the dam; the weight of
the structure; internal hydrostatic pressures (uplift) within the body
of the dam, at the base of the dam and within the foundation; earth and
silt loads; ice pressure, seismic and thermal loads, and other loads as
applicable. Where tailwater or backwater exists on the downstream side
of the structure it should be considered, and assumed uplift pressures
should be compatible with drainage provisions and uplift measurements if
available. Where applicable, ice pressure should be applied to the
contact surface of the structure of normal pool elevation. A unit
pressure of not more than 5,000 pounds per square foot should be used.
Normally, ice thickness should not be assumed greater than two feet.
Earthquake forces should consist of the inertial forces due to the
horizontal acceleration of the dam itself and hydrodynamic forces
resulting from the reaction of the reservoir water against the
structure. Dynamic water pressures for use in a conventional methods of
analysis may be computed by means of the ``Westergaard Formula'' using
the parabolic approximation (H.M. Westergaard, ``Water Pressures on Dams
During Earthquakes,'' Trans., ASCE, Vol 98, 1933, pages 418-433), or
similar method.
4.4.4.3. Stresses. The analysis of concrete stresses should be based
on in situ properties of the concrete and foundation. Computed maximum
compressive stresses for normal operating conditions in the order of \1/
3\ or less of in situ strengths should be satisfactory. Tensile stresses
in unreinforced concrete should be acceptable only in locations where
cracks will not adversely affect the overall performance and stability
of the structure. Foundation stresses should be such as to provide
adequate safety against failure of the foundation material under all
loading conditions.
4.4.4.4. Overturning. A gravity structure should be capable of
resisting all overturning forces. It can be considered safe against
overturning if the resultant of all combinations of horizontal and
vertical forces, excluding earthquake forces, acting above any
horizontal plane through the structure or at its base is located within
the middle third of the section. When earthquake is included the
resultant should fall within the limits of the plane or base, and
foundation pressures must be acceptable. When these requirements for
location of the resultant are not satisfied the investigating engineer
should assess the importance to stability of the deviations.
4.4.4.5. Sliding. Sliding of concrete gravity structures and of
abutment and foundation rock masses for all types of concrete dams
[[Page 294]]
should be evaluated by the shear-friction resistance concept. The
available sliding resistance is compared with the driving force which
tends to induce sliding to arrive at a sliding stability safety factor.
The investigation should be made along all potential sliding paths. The
critical path is that plane or combination of planes which offers the
least resistance.
4.4.4.5.1. Sliding resistance. Sliding resistance is a function of
the unit shearing strength at no normal load (cohesion) and the angle of
friction on a potential failure surface. It is determined by computing
the maximum horizontal driving force which could be resisted along the
sliding path under investigation. The following general formula is
obtained from the principles of statics and may be derived by resolving
forces parallel and perpendicular to the sliding plane:
[GRAPHIC] [TIFF OMITTED] TC15NO91.002
Where:
RR=Sliding Resistance (maximum horizontal driving force which
can be resisted by the critical path)
[phis]=Angle of internal friction of foundation material or, where
applicable, angle of sliding friction
V=Summation of vertical forces (including uplift)
c=Unit shearing strength at zero normal loading along potential failure
plane
A=Area of potential failure plane developing unit shear strength ``c''
[alpha]=Angle between inclined plane and horizontal (positive for uphill
sliding)
For sliding downhill the angle [alpha] is negative and Equation (1)
becomes:
[GRAPHIC] [TIFF OMITTED] TC15NO91.003
When the plane of investigation is horizontal, and the angle [alpha]
is zero and Equation (1) reduced to the following:
[GRAPHIC] [TIFF OMITTED] TC15NO91.004
4.4.4.5.2. Downstream esistance. When the base of a concrete
structure is embedded in rock or the potential failure plane lies below
the base, the passive resistance of the downstream layer of rock may
sometimes be utilized for sliding resistance. Rock that may be subjected
to high velocity water scouring should not be used. The magnitude of the
downstream resistance is the lesser of (a) the shearing resistance along
the continuation of the potential sliding plane until it daylights or
(b) the resistance available from the downstream rock wedge along an
inclined plane. The theoretical resistance offered by the passive wedge
can be computed by a formula equivalent to formula (3):
[GRAPHIC] [TIFF OMITTED] TC15NO91.005
Where:
Pp=Passive resistance of rock wedge
W=Weight (buoyant weight if applicable) of downstream rock wedge above
inclined plane of resistance, plus any superimposed loads
[phis]=Angle of internal friction or, if applicable, angle of sliding
friction
[alpha]=Angle between inclined failure plane and horizontal
c=Unit shearing strength at zero normal load along failure plane
A=Area of inclined plane of resistance
When considering cross-bed shear through a relatively shallow,
competent rock strut, without adverse jointing or faulting, W and
[alpha] may be taken at zero and 45[deg], respectively, and an estimate
of passive wedge resistance
[[Page 295]]
per unit width obtained by the following equation:
[GRAPHIC] [TIFF OMITTED] TC15NO91.006
Where:
D=Thickness of the rock strut
4.4.4.5.3. Safety factor. The shear-friction safety factor is
obtained by dividing the resistance RR by H, the summation of
horizontal service loads to be applied to the structure:
[GRAPHIC] [TIFF OMITTED] TC15NO91.007
When the downstream passive wedge contributes to the sliding
resistance, the shear friction safety factor formula becomes:
[GRAPHIC] [TIFF OMITTED] TC15NO91.008
The above direct superimposition of passive wedge resistance is
valid only if shearing rigidities of the foundation components are
similar. Also, the compressive strength and buckling resistance of the
downstream rock layer must be sufficient to develop the wedge
resistance. For example, a foundation with closely spaced, near
horizontal, relatively weak seams might not contain sufficient buckling
strength to develop the magnitude of wedge resistance computed from the
cross-bed shear strength. In this case wedge resistance should not be
assumed without resorting to special treatment (such as installing
foundation anchors). Computed sliding safety factors approximating 3 or
more for all loading conditions without earthquake, and 1.5 including
earthquake, should indicate satisfactory stability, depending upon the
reliability of the strength parameters used in the analyses. In some
cases when the results of comprehensive foundation studies are
available, smaller safety factors may be acceptable. The selection of
shear strength parameters should be fully substantiated. The bases for
any assumptions; the results of applicable testing, studies and
investigations; and all pre-existing, pertinent data should be reported
and evaluated.
Chapter 5--Reports
5.1. General. This chapter outlines the procedures for reporting the
results of the technical investigations. Hazardous conditions should be
reported immediately upon detection to the owner of the dam, the
Governor of the State in which the dam is located and the appropriate
regulatory agency without delay for preparation of the formal report.
5.2. Preparation of report. A formal report should be prepared for
each dam investigated for submission to the regulatory agency and the
owner of the dam. Each report should contain the information indicated
in the following paragraphs. The signature and registration
identification of the professional engineer who directed the
investigation and who was responsible for evaluation of the dam should
be included in the report.
5.2.1. Phase I reports. Phase I reports should contain the following
information:
5.2.1.1. Description of dam including regional vicinity map showing
location and plans, elevations and sections showing the essential
project features and the size and hazard potential classifications.
5.2.1.2. Summary of existing engineering data, including geologic
maps and information.
5.2.1.3. Results of the visual inspection of each project feature
including photographs and drawings to minimize descriptions.
5.2.1.4. Evaluation of operational adequacy of the reservoir
regulation plan and maintenance of the dam and operating facilities and
features that pertain to the safety of the dam.
5.2.1.5. Description of any warning system in effect.
5.2.1.6. Evaluation of the hydraulic and hydrologic assumptions and
structural stability.
5.2.1.7. An assessment of the general condition of the dam with
respect to safety based upon the findings of the visual inspection and
review of engineering data. Where data on the original design indicate
significant departure from or non-conformance with guidelines contained
herein, the engineer-in-charge of the investigation will give his
opinion of the significance, with regard to safety, of such factors. Any
additional studies, investigations and analyses considered essential to
assessment of the safety of the dam should be listed, together with an
opinion about the urgency of such additional work.
5.2.1.8. Indicate alternative possible remedial measures or
revisions in operating and maintenance procedures which may (subject to
further evaluation) correct deficiencies and hazardous conditions found
during the investigation.
5.2.2. Phase II reports. Phase II reports should describe the
detailed investigations and should supplement Phase I reports. They
should contain the following information:
5.2.2.1. Summary of additional engineering data obtained to
determine the hydraulic and hydrologic capabilities and/or structural
stability.
5.2.2.2. Results of all additional studies, investigations, and
analyses performed.
5.2.2.3. Technical assessment of dam safety including deficiences
and hazardous conditions found to exist.
5.2.2.4. Indicate alternative possible remedial measures or revision
in maintenance and operating procedures which may (subject
[[Page 296]]
to further evaluation) correct deficiencies and hazardous conditions
found during the investigation.
[GRAPHIC] [TIFF OMITTED] TC31OC91.017
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[GRAPHIC] [TIFF OMITTED] TC31OC91.018
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[GRAPHIC] [TIFF OMITTED] TC31OC91.019
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[GRAPHIC] [TIFF OMITTED] TC31OC91.020
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[GRAPHIC] [TIFF OMITTED] TC31OC91.021
Appendix I to App. D to Sec. 222.6--Engineering Data
This appendix lists engineering data which should be collected from
project records and, to the extent available, included in the
[[Page 301]]
Phase I investigation report. The list is intended to serve as a
checklist and not to establish rigid data requirements. Such a
compilation should also facilitate future inspections and
investigations. Only data readily available will be included in Phase I
reports, but data lacking and deemed necessary for an adequate safety
evaluation should be identified.
1. General Project Data.
a. Regional Vicinity Map showing the location of the dam, the
upstream drainage area and the downstream area subject to potential
damage due to failure of the dam and misoperation or failure of the
operating equipment.
b. As-Built Drawings indicating plans, elevations and sections of
the dam and appurtenant structures including the details of the
discharge facilities such as outlet works, limited service and emergency
spillways, flashboards, fuse plugs and operating equipment.
2. Hydrologic and Hydraulic Data including the following:
a. Drainage area and basin runoff characteristics (indicating
pending changes).
b. Elevation of top of conservation pool or normal upper retention
water surface elevation, as applicable (base level of any flood
impoundment).
c. Storage capacity including dead or inactive storage,
corresponding to top of conservation or normal upper retention level
(cumulative, excluding flood control and surcharge storage).
d. Elevation of the top of flood control pool.
e. Storage capacity of flood control zone (incremental).
f. Elevation of maximum design pool (corresponding to top of
surcharge storage or spillway design flood).
g. Storage capacity of surcharge zone (incremental, above top of
flood control pool or, above normal upper retention level if flood
control space not provided).
h. Height of freeboard (distance between maximum design flood water
surface and top of dam).
i. Elevation of top of dam (lowest point of embankment or non-
overflow structure).
j. Elevation of crest, type, width, crest length and location of
spillways (number, size and type of gates if controlled).
k. Type, location, entrance and exit inverts of outlet works and
emergency drawdown facilities (number, size and shape of conduits and
gates, including penstocks and sluices).
l. Location, crest elevation, description of invert and abutments
(concrete, rock, grass, earth) and length of limited service and
emergency spillways.
m. Location and dscription of flashboards and fuse plugs, including
hydraulic head (pool elevation) and other conditions required for
breaching, along with the assumed results of breaching.
n. Location and top elevation of dikes and floodwalls (overflow and
non-overflow) affected by reservoir. Include information on low reaches
of reservoir rim.
o. Type, location, observations and records of hydrometeorological
gages appurtenant to the project.
p. Maximum non-damaging discharge, or negligible damage rate, at
potential damage locations downstream.
3. Foundation Data and Geological Features including logs of
borings, geological maps, profiles and cross sections, and reports of
foundation treatment.
4. Properties of Embankments and Foundation Materials including
results of laboratory tests, field permeability tests, construction
control tests, and assumed design properties for materials.
5. Concrete Properties including the source and type of aggregate,
cement used, mix design data and the results of testing during
construction.
6. Electrical and Mechanical Equipment type and rating of normal and
emergency power supplies, hoists, cranes, valves and valve operator,
control and alarm systems and other electrical and mechanical equipment
and systems that could affect the safe operation of the dam.
7. Construction History including diversion scheme, construction
sequence, pertinent construction problems, alterations, modifications
and maintenance repairs.
8. Water Control Plan including regulation plan under normal
conditions and during flood events or other emergency conditions. The
availability of dam tenders, means of communication between dam tenders
and authority supervising water control, and method of gate operation
(manual, automatic, or remote control) should be included. Flood warning
systems should be described in sufficient detail to enable assessment of
their reduction in the flood hazard potential.
9. Operation Record.
a. Summary of past major flood events including any experiences that
presented a serious threat to the safety of the project or to human life
or property. The critical project feature, date and duration of event,
causative factor, peak inflow and outflow, maximum elevation of water
surface, wind and wave factors if significant, issuance of alert or
evacuation warnings and adequacy of project feature involved should be
included in the summary of past experience of serious threat to the
safety of the project.
b. Records of performance observations including instrumentation
records.
c. List of any known deficiencies that pose a threat to the safety
of the dam or to human life or property.
[[Page 302]]
d. History of previous failures or deficiencies and pending remedial
measures for correcting known deficiencies and the schedule for
accomplishing remedial measures should be indicated.
10. Earthquake History including a summary of the seismic data of
significant recorded earthquakes in the vicinity of the dam and
information on major damage in the vicinity of the dam from both
recorded and unrecorded earthquakes. Regional geologic maps and other
documents showing fault locations should be collected.
11. Inspection History including the results of the last safety
inspection, the organization that performed the inspection, the date
inspection performed and the authority for conducting the inspection.
12. Principal Design Assumptions and Analyses.
a. Hydrologic and Hydraulic Determinations.
(1) Quantity, time and area distribution, and reference source of
depth-area-duration data of spillway design storm precipitation (point
precipitation if applicable).
(2) Maximum design flood inflow hydrograph including loss rates
(initial and average for design flood conditions) and time of runoff
concentration of reservior watershed (peak inflow only when applicable).
(3) Maximum design flood outflow hydrograph (maximum outflow only
when applicable).
(4) Discharge-frequency relationship, preferably at damsite,
including estimated frequency of spillway design flood for small dams,
when appropriate.
(5) Reservior area and storage capacity versus water surface
elevation (table or curves).
(6) Rating curves (free flow and partial gate openings) for all
discharge facilities contributing to the maximum design flood outflow
hydrograph. Also a composite-rating of all contributing facilities, if
appropriate.
(7) Tailwater rating curve immediately below damsite including
elevation corresponding to maximum design flood discharge and
approximate nondamaging channel capacity.
(8) Hydrologic map of watershed above damsite including reservior
area, watercourse, elevation contours, and principal stream-flow and
precipitation gaging stations.
b. Stability and Stress Analysis of the dam, spillway and
appurtenant structures and features including the assumed properties of
materials and all pertinent applied loads.
c. Seepage and Settlement Analyses. The determination of
distribution, direction and magnitude of seepage forces and the design
and construction measures for their control. Settlement estimates and
steps adopted to compensate for total settlement and to minimize
differential settlements.
Appendix II to App. D to Sec. 222.6--Inspection Items
This appendix provides guidance for performing field inspections and
may serve as the basis for developing a detailed checklist for each dam.
1. Concrete Structures in General.
a. Concrete Surfaces. The condition of the concrete surfaces should
be examined to evaluate the deterioration and continuing serviceability
of the concrete. Descriptions of concrete conditions should conform with
the appendix to ``Guide for Making a Condition Survey of Concrete in
Service,'' American Concrete Institute (ACI) Journal, Proceedings Vol.
65, No. 11, November 1968, page 905-918.
b. Structural Cracking. Concrete structures should be examined for
structural cracking resulting from overstress due to applied loads,
shrinkage and temperature effects or differential movements.
c. Movement--Horizontal and Vertical Alignment. Concrete structures
should be examined for evidence of any abnormal settlements, heaving,
deflections, or lateral movements.
d. Junctions. The conditions at the junctions of the structure with
abutments or embankments should be determined.
e. Drains--Foundation, Joint, Face. All drains should be examined to
determine that they are capable of performing their design function.
f. Water Passages. All water passages and other concrete surfaces
subject to running water should be examined for erosion, cavitation,
obstructions, leakage or significant structural cracks.
g. Seepage or Leakage. The faces, abutments and toes of the concrete
structures should be examined for evidence of seepage or abnormal
leakage, and records of flow of downstream springs reviewed for
variation with reservoir pool level. The sources of seepage should be
determined if possible.
h. Monolith Joints--Construction Joints. All monolith and
construction joints should be examined to determine the condition of the
joint and filler material, any movement of joints, or any indication of
distress or leakage.
i. Foundation. Foundation should be examined for damage or possible
undermining of the downstream toe.
j. Abutments. The abutments should be examined for sign of
instability or excessive weathering.
2. Embankment Structures.
a. Settlement. The embankments and downstream toe areas should be
examined for any evidence of localized or overall settlement,
depressions or sink holes.
b. Slope Stability. Embankment slopes should be examined for
irregularities in
[[Page 303]]
alignment and variances from smooth uniform slopes, unusual changes from
original crest alignment and elevation, evidence of movement at or
beyond the toe, and surface cracks which indicate movement.
c. Seepage. The downstream face of abutments, embankment slopes and
toes, embankment--structure contacts, and the downstream valley areas
should be examined for evidence of existing or past seepage. The sources
of seepage should be investigated to determine cause and potential
severity to dam safety under all operating conditions. The presence of
animal burrows and tree growth on slopes which might cause detrimental
seepage should be examined.
d. Drainage Systems. All drainage systems should be examined to
determine whether the systems can freely pass discharge and that the
discharge water is not carrying embankment or foundation material.
Systems used to monitor drainage should be examined to assure they are
operational and functioning properly.
e. Slope Protection. The slope protection should be examined for
erosion-formed gullies and wave-formed notches and benches that have
reduced the embankment cross-section or exposed less wave resistant
materials. The adequacy of slope protection against waves, currents, and
surface runoff that may occur at the site should be evaluated. The
condition of vegetative cover should be evaluated where pertinent.
3. Spillway Structures. Examination should be made of the structures
and features including bulkheads, flashboards, and fuse plugs of all
service and auxiliary spillways which serve as principal or emergency
spillways for any condition which may impose operational constraints on
the functioning of the spillway.
a. Control Gates and Operating Machinery. The structural members,
connections, hoists, cables and operating machinery and the adequacy of
normal and emergency power supplies should be examined and tested to
determine the structural integrity and verify the operational adequacy
of the equipment. Where cranes are intended to be used for handling
gates and bulkheads, the availability, capacity and condition of the
cranes and lifting beams should be investigated. Operation of control
systems and protective and alarm devices such as limit switches, sump
high water alarms and drainage pumps should be investigated.
b. Unlined Saddle Spillways. Unlined saddle spillways should be
examined for evidence of erosion and any conditions which may impose
constraints on the functioning of the spillway. The ability of the
spillway to resist erosion due to operation and the potential hazard to
the safety of the dam from such operation should be determined.
c. Approach and Outlet Channels. The approach and outlet channels
should be examined for any conditions which may impose constraints on
the functioning of the spillway and present a potential hazard to the
safety of the dam.
d. Stilling Basin (Energy Dissipators). Stilling basins including
baffles, flip buckets or other energy dissipators should be examined for
any conditions which may pose constraints on the ability of the stilling
basin to prevent downstream scour or erosion which may create or present
a potential hazard to the safety of the dam. The existing condition of
the channel downstream of the stilling basin should be determined.
4. Outlet Works. The outlet works examination should include all
structures and features designed to release reservoir water below the
spillway crest through or around the dam.
a. Intake Structure. The structure and all features should be
examined for any conditions which may impose operational constraints on
the outlet works. Entrances to intake structure should be examined for
conditions such as silt or debris accumulation which may reduce the
discharge capabilities of the outlet works.
b. Operating and Emergency Control Gates. The structural members,
connections, guides, hoists, cables and operating machinery including
the adequacy of normal and emergency power supplies should be examined
and tested to determine the structural integrity and verify the
operational adequacy of the operating and emergency gates, valves,
bulkheads, and other equipment.
c. Conduits, Sluices, Water Passages, Etc. The interior surfaces of
conduits should be examined for erosion, corrosion, cavitation, cracks,
joint separation and leakage at cracks or joints.
d. Stilling Basin (Energy Dissipator). The stilling basin or other
energy dissipator should be examined for conditions which may impose any
constraints on the ability of the stilling basin to prevent downstream
scour or erosion which may create or present a potential hazard to the
safety of the dam. The existing condition of the channel downstream of
the stilling basin should be determined by soundings.
e. Approach and Outlet Channels. The approach and outlet channels
should be examined for any conditions which may impose constraints on
the functioning of the discharge facilities of the outlet works, or
present a hazard to the safety of the dam.
f. Drawdown Facilities. Facilities provided for drawdown of the
reservoir to avert impending failure of the dam or to facilitate repairs
in the event of stability or foundation problems should be examined for
any conditions which may impose constraints on their functioning as
planned.
5. Safety and Performance Instrumentation. Instruments which have
been installed to measure behavior of the structures should be
[[Page 304]]
examined for proper functioning. The available records and readings of
installed instruments should be reviewed to detect any unusual
performance of the instruments or evidence of unusual performance or
distress of the structure. The adequacy of the installed instrumentation
to measure the performance and safety of the dam should be determined.
a. Headwater and Tailwater Gages. The existing records of the
headwater and tailwater gages should be examined to determine the
relationship between other instrumentation measurements such as stream
flow, uplift pressures, alignment, and drainage system discharge with
the upper and lower water surface elevations.
b. Horizontal and Vertical Alignment Instrumentation (Concrete
Structures). The existing records of alignment and elevation surveys and
measurements from inclinometers, inverted plumb bobs, gage points across
cracks and joints, or other devices should be examined to determine any
change from the original position of the structures.
c. Horizontal and Vertical Movement, Consolidation, and Pore-Water
Pressure Instrumentation (Embankment Structures). The existing records
of measurements from settlement plates or gages, surface reference
marks, slope indicators and other devices should be examined to
determine the movement history of the embankment. Existing piezometer
measurements should be examined to determine if the pore-water pressures
in the embankment and foundation would under given conditions impair the
safety of the dam.
d. Uplift Instrumentation. The existing records of uplift
measurements should be examined to determine if the uplift pressures for
the maximum pool would impair the safety of the dam.
e. Drainage System Instrumentation. The existing records of
measurements of the drainage system flow should be examined to establish
the normal relationship between pool elevations and discharge quantities
and any changes that have occurred in this relationship during the
history of the project.
f. Seismic Instrumentation. The existing records of seismic
instrumentation should be examined to determine the seismic activity in
the area and the response of the structures of past earthquakes.
6. Reservoir. The following features of the reservoir should be
examined to determine to what extent the water impounded by the dam
would constitute a danger to the safety of the dam or a hazard to human
life or property.
a. Shore line. The land forms around the reservoir should be
examined for indications of major active or inactive landslide areas and
to determine susceptibility of bedrock stratigraphy to massive
landslides of sufficient magnitude to significantly reduce reservoir
capacity or create waves that might overtop the dam.
b. Sedimentation. The reservoir and drainage area should be examined
for excessive sedimentation or recent developments in the drainage basin
which could cause a sudden increase in sediment load thereby reducing
the reservoir capacity with attendant increase in maximum outflow and
maximum pool elevation.
c. Potential Upstream Hazard Areas. The reservoir area should be
examined for features subject to potential backwater flooding resulting
in loss of human life or property at reservoir levels up to the maximum
water storage capacity including any surcharge storage.
d. Watershed Runoff Potential. The drainage basin should be examined
for any extensive alterations to the surface of the drainage basin such
as changed agriculture practices, timber clearing, railroad or highway
construction or real estate developments that might extensively affect
the runoff characteristics. Upstream projects that could have impact on
the safety of the dam should be identified.
7. Downstream Channel. The channel immediately downstream of the dam
should be examined for conditions which might impose any constraints on
the operation of the dam or present any hazards to the safety of the
dam. Development of the potential flooded area downstream of the dam
should be assessed for compatibility with the hazard classification.
8. Operation and Maintenance Features.
a. Reservoir Regulation Plan. The actual practices in regulating the
reservoir and discharges under normal and emergency conditions should be
examined to determine if they comply with the designed reservoir
regulation plan and to assure that they do not constitute a danger to
the safety of the dam or to human life or property.
b. Maintenance. The maintenance of the operating facilities and
features that pertain to the safety of the dam should be examined to
determine the adequacy and quality of the maintenance procedures
followed in maintaining the dam and facilities in safe operating
condition.
Appendix III to App. D to Sec. 222.6--Pub. L. 92-367
[[Page 305]]
[GRAPHIC] [TIFF OMITTED] TC31OC91.022
[[Page 306]]
[GRAPHIC] [TIFF OMITTED] TC31OC91.023
Appendix E to Sec. 222.6--Suggested Outline
Inspection Report--National Dam Inspection Program (RCS-DAEN-CWE-17 and
OMB No. 49-R0421)
Title Sheet
Name of Dam
ID Number from Inventory
State, County and River or Stream where dam is located
Owner
Size and Hazard Classification
Names of Inspectors
Names of Review Board
Approval Signature of District Engineer
Table of Contents
General Assessment
Give brief assessment of general condition of dam with respect to
safety, including a listing of deficiencies, and recommendations
indicating degree of urgency.
1. Introduction
a. Authority
b. Purpose and Scope of Inspection
2. Project Information
a. Site Information
b. Description of Structures--Dam, Outlet, Spillway and other
principal features.
c. Purpose of Dam
d. Design, Construction and Operating History
3. Field Inspection
Briefly describe physical condition of the dam and appurtenant
structures as they were observed during the field inspection. (If field
inspection form is appended, only present summary.) Describe operational
procedures, including any warning system, condition of operating
equipment, and provision for emergency procedures. Describe any
pertinent observations of the reservoir area and downstream channel
adjacent to dam.
[[Page 307]]
4. Evaluation
a. Structural and Geotechnical
(1) General
(2) Embankment and/or Foundation Condition
(3) Stability--Briefly discuss pertinent information such as design,
construction and operating records. Assess stability under maximum
loading on basis of the record data, together with observations of field
inspection and results of any additional, brief calculations performed
by inspectors. If additional, detailed stability analyses are considered
necessary, recommend that the owner engage a qualified engineer or firm
to provide the analysis.
b. Hydrologic and Hydraulic
(1) Spillway Adequacy--Briefly describe pertinent record information
such as hydrologic and hydraulic design data, flood of record, and
previous analyses. Describe any hydraulic and hydrologic analyses made
for this inspection. Present conclusion with respect to adequacy of
spillway to pass the recommended spillway design flood without
overtopping dam. If overtopping would occur, and if available from the
type of analysis used, give maximum depth over top of dam and duration
of overtopping, assuming the dam does not fail. Also indicate the
largest flood, as a percentage of the probable maximum flood which can
be passed without overtopping.
(2) Effects of overtopping--If dam is overtopped by the recommended
spillway design flood, provide assessment as to whether or not dam would
likely fail, and if, in case of failure, the hazard to loss of life
downstream of the dam would be substantially increased over that which
would exist without failure. If information upon which to base a
reasonable assessment is insufficient, so state and describe the needed
data, and recommend that the necessary studies be performed by engineers
engaged by the owner.
c. Operation and Maintenance
Assess operating equipment and procedures, emergency power for gate
operation, and Emergency Action Plan. Assess quality of maintenance as
it pertains to dam safety.
5. Conclusions
Provide conclusions on condition of dam and list all deficiencies.
If dam is considered unsafe, so state and give reason.
6. Recommendations
List all recommended actions, including additional studies,
installation of new surveillance procedures and devices, development of
Emergency Action Plans, and remedial work. Recommend that a qualified
engineering firm be retained to accomplish any recommended additional
investigations and studies and also to design and supervise remedial
works.
Appendixes
a. Inspection Checklist (if available)
b. Other Illustrations as follows:
(1) Include a map showing location of the dam. Usually a portion of
a USGS quadrangle sheet can be used which will show the topography of
the area, location of the dam, exent of the lake and drainage basin, and
perhaps indicate the downstream development.
(2) If available, include a plan and section of the dam.
(3) General photographs of the dam and downstream channel should be
included.
(4) Color photographs of deficiencies should be included. These
should be held to the minimum required to illustrate the deficiencies.
(5) Available engineering data including Hydrologic/Hydraulic
calculation and physical test results that might be available.
Appendix F to Sec. 222.6
Instructions for Unsafe Dam Data Sheet (RCS-DAEN-CWE-17 and OMB No. 49-
R0421)
The indicated information shall be provided in the format shown on
Pg F-3 for each dam assessed to be unsafe during the reporting period. A
separate data sheet should be provided for each unsafe dam. The
information supplied should conform to the following.
a. Name--Name of dam.
b. Id. No.--Dam inventory identity number.
c. Location--List state county, river or stream and nearest D/S city
or town where the dam is located.
d. Height--Maximum hydraulic height of dam.
e. Maximum Impoundment Capacity--List the capacity of the reservior
at maximum attainable water surface elevation including any surcharge
loading.
f. Type--Type of dam, i.e., earth, rockfill, gravity, combination
earth-gravity, etc.
g. Owner--Owner of dam.
h. Date Governor Notified of Unsafe Condition--The date and method
of notification, such as, by telegram, letter, report, etc.
i. Condition of Dam Resulting in Unsafe Assessment--Brief
description of the deficiencies discovered which resulted in the unsafe
assessment.
j. Description of Danger Involved--Downstream (D/S) hazard potential
category and a brief description of the danger involved.
k. Recommendations Given to Governor--Brief description of the
actions recommended to Governor at time of notification of unsafe
condition to eliminate or reduce the danger.
l. Urgency Category--State whether the unsafe condition of the dam
is an emergency or non-emergency situation. An emergency situation
should be considered to exist if the failure of the dam is judged to be
imminent
[[Page 308]]
and requires immediate action to eliminate or reduce the danger.
m. Emergency Actions Taken--In case of an emergency situation, list
the actions taken. For non-emergency situation, put NA for ``not
applicable.''
n. Remedial Action Taken--For non-emergency situations list remedial
actions taken.
o. Remarks--For other pertinent information.
Format for Unsafe Dam Data Sheet (RCS-DAEN-CWE-17 and OMB No. 49-R0421
National Program of Inspection of Non-Federal Dams--Unsafe Dam Data
Sheet
a. Name:
b. Type:
c. Height:
d. Id. No.
e. Location:
State: County:
Nearest D/S City, Town or Village:
River or Stream:
f. Owner:
g. Date Governor Notified of Unsafe Condition:
h. Condition of Dam Resulting in Unsafe Assessment:
i. Description of Danger Involved:
j. Recommendations Given to Governor:
k. Urgency Category:
l. Emergency Actions Taken:
m. Remarks:
Appendix G to Sec. 222.6
National Program for Inspection of Non-Federal Dams--Monthly Progress
Report (RCS-DAEN-CWE-19)
I. Instructions for Monthly Progress Report. The indicated information
shall be provided in the format shown on page G-2.
1. Division Reporting:
2. Date:
3. Information Required for Each State Regarding Total Number of
Inspections Performed (AE Inspections included) (Cumulative):
3.1. Number of Inspections Initiated by on-site inspection or the
review of engineering data from project records. \1\
---------------------------------------------------------------------------
\1\ Each of the initiated inspections reported should be planned for
completion within a reasonable period of time (30 days.)
---------------------------------------------------------------------------
3.2. Number of Inspections Competed (The number of inspection
reports which have been submitted to the District Engineer for review
and approval).
3.3 Number of Dams Reported to the Governor as Unsafe. \2\
---------------------------------------------------------------------------
\2\ An unsafe dam is defined as a dam with deficiencies of such a
nature that if not corrected could result in the failure of the dam with
subsequent loss of lives or substantial property damage.
---------------------------------------------------------------------------
3.4. Number of Approved Inspection Reports Submitted to the
Governor.
4. Information Required for Each State Regarding Inspections
Performed Under AE Contracts (Cumulative):
4.1. Number of Dams Contracted for Inspection by AE's with State or
Corps.
4.2. Number of Inspections Initiated by AE's by on-site inspection
or the review of engineering data from project records. \1\
---------------------------------------------------------------------------
\1\ See footnote on previous page.
---------------------------------------------------------------------------
4.3. Number of Inspections Completed by AE's (The number of
inspection reports which have been submitted to the District Engineer
for review and approval).
4.4. Number of Approved Inspection Reports Prepared by AE's
Submitted to the Governor.
II. Formation for Monthly Progress Report.
National Program for Inspection of Non-Federal Dams--Monthly Progress
Report
1. Division Reporting:
2. Date:
3. Information Required for Each State Regarding Total Number of
Inspections Performed (Cumulative):
------------------------------------------------------------------------
Unsafe
Inspection Inspection Dams Approved
State Initiated Completed Reported Reports
(3.1) (3.2) (3.3) (3.4)
------------------------------------------------------------------------
===========================================
Total.......................
------------------------------------------------------------------------
4. Information Required for Each State Regarding Inspections
Performed Under A/E Contracts (Cumulative):
----------------------------------------------------------------------------------------------------------------
Dams
Under A/ A/E A/E A/E
State E Inspections Inspections Reports
Contract Initiated Completed Approved
(4.1) (4.2) (4.3) (4.4)
----------------------------------------------------------------------------------------------------------------
=============================================
Totals............................................................
----------------------------------------------------------------------------------------------------------------
Appendix H to Sec. 222.6
Suggested Scope of Work Contract for Architect-Engineer Services for
Safety Inspection of Dams Within the State of --------
1. General Description of Scope of Work. The services to be rendered
by the Architect-Engineer (AE) under the proposed contract
[[Page 309]]
shall include all engineering functions, hereinafter described, as
needed to inspect the dams listed in Appendix A of this contract for the
purpose of evaluating their risk of failure. A report which (a)
describes the assessed condition of the dam, (b) provides conclusions as
to which particular conditions could cause failure, (c) makes
recommendations on remedial measures believed necessary, and (d) makes
recommendations on whether and what type of future investigation should
be conducted shall be provided for each inspected dam. The work shall
proceed in accordance with Phase I of the Recommended Guidelines for
Safety Inspection of Dams established by the Office of the Chief of
Engineers (OCE) and the supplemented requirements listed in paragraph 3
below. The OCE guidelines are listed in Appendix B of this contract.
2. Information and Services To Be Furnished by the Government. The
Contracting Officer will furnish the following information and services
to the AE:
a. All information pertaining to each dam to be inspected as
contained in the National Inventory of Dams.
b. Copies of recommended format for preparation of inspection
report, engineering data check list and visual inspection check list.
c. All available pertinent information pertaining to the Dam
Inspection Program and previous investigations having a bearing on
inspections to be performed under this contract.
d. Right-of-entry for access to each dam site.
3. Services To Be Rendered by the Architect-Engineer. The principal
services, subject to the optional provisions of the contract, to be
rendered by the AE are itemized below:
a. Technical Investigations.
(1) Engineering Data Collection. To the extent feasible, the
engineering data listed in Appendix I of the OCE guidelines relating to
the design, construction and operation of the dam and appurtenant
structures, should be collected from existing records and reviewed to
aid in evaluating the general condition of each dam, including an
assessment of the hydraulic and hydrologic features and structural
stability of the dam. Where the necessary engineering data are
unavailable, inadequate or invalid, a listing shall be made of those
specific additional data deemed necessary by the engineer in charge of
the investigation and included in the inspection report. The engineering
data checklist provided by the Contracting Officer shall be used as a
guide to compile this data.
(2) Field Inspections. The field inspection of each dam shall
include examination of the items listed in Appendix II of the OCE
guidelines, electrical and mechanical equipment for operation of the
control facilities, reservoir area, downstream channel in the vicinity
of the dam and any other significant feature to determine how these
features affect the risk of failure of the dam. The inspection shall be
conducted in a systematic manner to minimize the possibility of any
significant feature being overlooked. The visual inspection checklist
provided by the Contracting Officer shall be used as a guide to document
the examination of each significant feature.
Particular attention shall be given to detecting evidence of
leakage, erosion, seepage, slope instability, undue settlement,
displacement, tilting, cracking, deterioration, and improper functioning
of drains and relief wells. The degree and quality of maintenance and
regulating procedures for operation of the control facilities shall be
assessed. The design and existing condition of such control facilities
(i.e., spillway, outlet works, etc.) shall be evaluated. An assessment
of the degree of siltation that is evident and its effect on the dam's
reservoir shall be performed. Photographs and drawings should be used to
record conditions in order to minimize written descriptions.
(3) Engineering Analyses.
(a) Evaluation of Hydraulic and Hydrologic (H&H) Features.
Evaluation of the hydraulic and hydrological features of each dam shall
be based on criteria set forth in the OCE guidelines. If it is
determined that the available H&H data are insufficient, the Contracting
Officer must be so informed and may exercise an option of requiring the
AE to perform an overtopping analysis at additional agreed-upon
compensation. The methodology to be used by the AE for this analysis
will be based on the OCE guidelines and subject to the approval of the
Contracting Officer.
(b) Evaluation of Structural Stability. The evaluation of structural
stability of each dam is to be based principally on existing conditions
as revealed by the visual inspection, available design and construction
information, and records of performance. The objectives are to determine
the existence of conditions, identifiable by visual inspection or from
records, which may pose a high risk of failure and to formulate
recommendations pertaining to the need for any remedial improvements,
additional studies, investigations, or analysis. The results of this
phase of the inspection must rely substantially upon the experience and
judgment of the inspecting engineer. Should it be determined that
sufficient data are not available for a reasonable evaluation of the
structural stability of a dam and appurtenances, the Contracting Officer
should be informed which information is required prior to attempting to
evaluate the risk of failure of the dam.
(c) Evaluation of Operational Features. Where critical mechanical/
electrical operating equipment is used in controlling the
[[Page 310]]
reservoir of a dam, an evaluation of the operational characteristics of
this equipment from the standpoint of risk of failure must be performed.
(d) Evaluation of Reservoir Regulation Plan and Warning System. The
operational characteristics of each dam's existing reservoir regulation
plan and warning system in event of a threatened failure shall be
investigated.
b. Emergency Situations. The Contracting Officer must be immediately
notified of any observed condition which is deemed to require immediate
remedial action. After being notified, the Contracting Officer will
contact the appropriate State personnel and will meet the AE at the site
to determine the appropriate course of action. This will not relieve the
AE of his responsibility to prepare a comprehensive inspection report at
the earliest practicable date.
c. Qualifications of Investigators. The technical investigations
shall be conducted by licensed professional engineers with a minimum of
five years experience after licensing in the investigation, design and
contruction of earthfill, rockfill and concrete dams and/or in making
risk of failure evaluations of completed dams. These engineers must be
knowledgeable in the disciplines of hydrology, hydraulics, geotechnical,
electrical, mechanical and structural engineering, as necessary. All
field inspections should be conducted by engineers, engineering
geologists and other specialists who are knowledgeable in the
investigation, design, construction and operation of dams, including
experts on mechanical and electrical operation of gates and controls,
where needed.
d. Preparation of Report. A formal report shall be prepared for each
dam inspected for submission to the Contracting Officer. Each report
should contain the information specified in OCE guidelines and any other
pertinent information. The recommended format provided by the
Contracting Officer shall be used to document each report. The signature
and registration identification of the professional engineer who
directed the investigation and who was responsible for evaluation of the
dam should be included in the report.
4. Supervision and Approval of Work. All work performed under this
contract shall be subject to the review and approval of the Contracting
Officer or his designee. Meetings will be held on a regular basis in the
District office, during which the progress of inspections will be
discussed and questions relating to inspection reports previously
received by the Contracting Officer will be addressed. Reports will be
revised as necessary when required by the Contracting Officer.
5. Coordination. During the progress of work, the AE shall maintain
liaison with the *-------- and other local authorities through the
Contracting Officer as required to assure the orderly progression of the
inspection. Copies of all correspondence with such authorities shall be
provided to the Contracting Officer.
---------------------------------------------------------------------------
* Note: Write in the designated State Authority.
---------------------------------------------------------------------------
6. Submission of Report.
a. Each inspection report will be submitted for review to the
Contracting Officer. Reports will be revised as required by the
Contracting Officer. After all revisions have been made, the original
and ---- copies of each inspection report shall be submitted to the
Contracting Officer.
b. Text of all reports shall be typewritten and printed on both
sides of 8x10\1/2\ paper. All notes, inspection
forms, sketches or similar matter shall be legible, distinct and
suitable for reproduction.
7. Period of Services.
a. All inspections and reports included under this contract shall be
completed within ---- days from date of Notice to Proceed.
b. If the option for performing an H&H analysis for any particular
site is exercised, the AE shall complete such analysis within ---- days
from date of Notice to Proceed. However, the overall completion time
stated in paragraph 7a above shall not change.
Appendix I to Sec. 222.6
Procedure for Using NASA Land Satellite Multispectral Scanner Data for
Verification and Updating the National Inventory of Dams
1. Purpose. This appendix states the objective, defines the scope,
prescribes procedures, and assigns responsibilities for using NASA Land
Satellite (LANDSAT) Multispectral Scanner data along with NASA's Surface
Water Detection And Mapping (DAM) Computer program to assist in
verification and updating the National Inventory of Dams.
2. Applicability. This appendix is applicable to all divisions and
districts having Civil Works responsibilities except POD.
3. Reference. NASA, DETECTION AND MAPPING PACKAGE, Users Manuals,
Volumes 1, 2a, 2b, and 3 dated June 1976, published by the Johnson Space
Center, Houston, Texas.
4. Objectives. Provide a uniform method, nation-wide, to help insure
that all dams subject to Public Law 92-367, 8 August 1972 are properly
identified and located in the National Inventory of Dams.
5. Scope. The computer printer overlay maps produced by the
procedure described in reference 3b will be used by district and/or
state or contractor personnel as a tool to assist in verification and
updating of the National Inventory of Dams.
[[Page 311]]
6. Exceptions. a. If a Division/District attempts the use of the
procedure for a given region within their area of responsibility and
finds the overlay maps cannot be used to assist in verification and
updating the National Inventory of Dams, they may request an exception
for a selected region. A selected region may include areas where
conditions can reasonably be assumed to be the same as the region where
the procedure was tried.
b. Request for exceptions should be documented to include firm
boundary definitions and appropriate justification to demonstrate why
the procedure cannot be used. This request should be submitted to WRSC
WASH DC 20314, through the normal engineering chain of command.
c. Map overlays will be produced for all areas of the Continental
United States even if they are not used in a few selected regions. This
processing is required for a future Computer Water Body Change Detection
system.
7. Procedures. Acquisition of LANDSAT data, registration of
satellite coordinates to earth latitude and longitude and computer
processing to produce overlay maps will be accomplished by two Regional
Centers. Nashville District and Seattle District have been designated as
the Regional Centers, with each responsible for processing maps by state
based on Divisional assignments in Appendix A. Regional Centers will
support divisions as follows:
------------------------------------------------------------------------
Regional Center Division
------------------------------------------------------------------------
Nashville District New England
North Atlantic
South Atlantic
Ohio River
Lower Mississippi Valley
North Central
Seattle District Southwestern
Missouri River
North Pacific
South Pacific
------------------------------------------------------------------------
8. Responsibilities. a. The Water Resources Support Center at Fort
Belvoir has overall responsibility for coordination and monitoring of
this activity between NASA, Division Offices, and Regional Centers, and
for providing Regional Center funding.
b. Regional Centers are responsible for:
(1) Acquiring proper LANDSAT data tape from EROS Data Center (Sioux
Falls, South Dakota). Actual data scene selection will be coordinated
with Division and/or District to insure proper consideration is given to
local priorities and seasonal coverage.
(2) Arranging computer processing support using NASA's DAM package.
(3) Establishing proper control between satellite scanner-oriented
coordinates and earth latitude/longitude.
(4) Producing total coverage of map overlays at a scale of 1:24,000
and/or smaller scales as required by Divisions and/or Districts.
(5) Instructing District, State, or contractor personnel in the
assembly and use of map overlays.
c. Divisions/Districts are responsible for:
(1) Designating one person from each Division and District as the
point of contact with the Regional Center and provide this person's name
and phone number to the Regional Center.
(2) Providing the Regional Center with map coverage of their area of
responsibility. This will include state indexes and 7\1/2\ minute
quadrangle sheets (scale 1:24,000) where available.
(3) Coordinating with the Regional Center in selecting LANDSAT data
tapes.
(4) Providing information to Regional Center on scale and priorities
of desired computer produced map overlays.
(5) Assembling computer print-outs into overlay maps, and using as
appropriate to assist in verification and updating the National
Inventory of Dams.
9. Points of Contact. The points of contact in the Regional Centers
for this program are as follows:
Name, Office Symbol, and Telephone
Jim Cook--DAEN-ORNED, (615) 251-7366; FTS 852-7366.
Jack Erlandson--DAEN-NPSEN, (206) 764-3535; FTS 399-3535.
[44 FR 55336, Sept. 26, 1979, as amended at 45 FR 18925, Mar. 24, 1980.
Redesignated at 60 FR 19851, Apr. 21, 1995]