EP 1165-2-1
30 Jul 99
Act. Decisions regarding project modifications are made on an
individual case basis. Questionable cases are reported to HQUSACE in
a PAC report (if not as one subject in a routine precontruction
planning document of broader project coverage) with the views and
recommendations of the division and district commander.
Recommendations for modifications beyond the authority delegated to
the Chief of Engineers are submitted to the ASA(CW) with supporting
documentation suitable to the case, for review and subsequent
transmittal to Congress for authorization.
9-4. Design Sizing of Projects. The basic scope of projects is
established in the project authorization and, if necessary, reaffirmed
in a subsequent Design Memorandum or other post-authorization report.
Modification of the project from authorized dimensions may require
additional authorization in accordance with paragraph 9-3.
a. Flood Control. Flood damage reduction projects are
authorized to provide a specific "degree of protection" with a given
"degree of certainty". The "degree of protection" and the certainty
with which it is provided for a particular project is the measure of
flood severity and the certainty for its elimination of detrimental
flood effects downstream from a reservoir or within the confines of a
local flood protection project. This type of presentation gives the
decision makers the opportunity to assess the degree of protection and
the costs associated with increasing the certainty of obtaining the
degree of protection desired. Risk based analysis is an approach to
evaluation and decision making that explicitly, and to the extent
practical, analytically, incorporates considerations of risk and
uncertainty in the engineering and economic analysis of a project.
Such analyses are particularly useful in evaluating levees and
floodwalls, where the consequences of an overtopping may be severe and
the benefits of increasing the certainty of protection may make such
action desirable.
b. Navigation. Navigation projects are generally authorized to
provide a channel of specific dimensions. In accordance with Section
5 of the River and Harbor Act of 1915 channel depths generally signify
the depth at mean low water in tidal waters tributary to the Atlantic
and Gulf coasts, at mean lower low water in tidal waters tributary to
the Pacific coast, and the mean depth for a continuous period of 15
days of the lowest water in the navigation season of any year in
rivers and non-tidal channels. Authorized channel dimensions are
understood to permit increase at entrances, bends, sidings and turning
places to allow free movement of vessels. Authorized channel depths
include allowances for vessel draft, squat, roll, pitch, yaw and
underkeel clearance. (EM 1110-2-1607, ER 1110-2-1403, 1457, 1458)
9-5. Aesthetic Treatment and Environmental Design. All project
features are designed so that the visual and human-cultural values
associated with the project will be protected, preserved, or
maintained to the maximum extent practicable. Specific ecological
considerations include actions to preserve critical habitats of fish
and wildlife; accomplish sedimentation and erosion control; maintain
water quality; regulate streamflow, runoff and groundwater supplies;
and avoidance or mitigation of actions whose effect would be to reduce
scarce biota, ecosystems, or basic resources. In the development of
individual project features, consideration is given to the needs for
architectural design, land treatment or other resource conservation
measures. Emphasis is given to developing measures for realizing the
full scenic potential of the project feature as it affects the overall
project. This is accomplished by providing for cover reforestation,
9-3
Previous Page
