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WEB-BASED HANDBOOK (Legacy Edition). CLICK HERE to submit comments.
Because of staff changes and Randolph Langenbach's retirement from FEMA, these handbooks were never published on the FEMA website.  These are the only copies available.


 

Chapter 5: UTILITIES 

A. High Velocity Flows

 

Introduction

Problem:

High velocity flows can scour and erode soils, which undermine a utility's support.

Mitigation Objective:

Protect the utility facility from high velocity flows that can erode soils away from the utility, leaving it vulnerable to flood damage

A.1 Relocate Utility

Relocate the utility to a safe location away from the hazard. Also consider burying the utility.

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Effectiveness:

  • Very effective

Limitations:

  • New location should be free of other hazards, such as exposure to high winds and unstable slopes.

Considerations:

A.2 Elevate Utility

Elevate and/or seal vulnerable components of the utility system, including electrical components and access points, above the design flood elevation.

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Effectiveness:

  • Very effective in preventing floodwaters from entering the systems, such as: electrical control panels, transformers and switches, and utility access points.

Limitations:

  • May require shutdown of the facility.
  • May inhibit maintenance access.
  • May not be feasible in areas of deep flooding or in urbanized areas.

Considerations:

A.3 Encase the Utility

Encase utility lines, such as electrical, communication, gas and water transmission and distribution lines in concrete and/or conduit to protect them from the damaging effects of floodwaters, including scouring.

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Effectiveness:

  • Very effective

Limitations:

  • May not be feasible in areas with fine soils subject to high velocity flows, or where extensive erosion is common.

    Maintenance access may be significantly restricted

    Utility lines could be vulnerable to earthquakes, slides, or other earth movement events.

Considerations:

 

 

NOTE:  None of the mitigation measures in these Handbooks should be considered ‘pre-approved’ or otherwise automatically eligible for FEMA funding. Only FEMA staff can determine eligibility, once they have determined that an applicant is eligible and they have reviewed a project proposal.

FEMA HAZARD MITIGATION HANDBOOKS                                                                        Updated: June 13, 2002