FLOOD02368

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Office of the State engineer Rules and Regulation for Dam Safety Construction
• Date: 8/26/1988
• Prepared For: State of Colorado
• Prepared By: Office of The State Engineer
• Floodplain - Doc Type: Educational/Technical/Reference Information

5. Minimum compacted densities for embankment materials
shall be 95 percent of maximum dry density for ASTM 0-698 (Standard
Proctor) or 90 percent for ASTM 01557 (Modified Proctor), as found in
the 1986 "Annua 1 Book of . ASTM Standards", Sect ion 04.08, So il and
Rock; Building Stones, 1916 Race Street, Philadelphia, Pennsylvania,
19103, which is hereby incorporated by reference into this rule, and
does not include later amendments to, or editions of, the incorporated
material, Impervious zones with clay fines shall be controlled using
Standard Proctor criteria to maintain the plastic nature of the
material; and

6. The minimum density for cohesionless materials shall be
70 percent relative density as determined by ASTM 0-4253 and 4254 as
found in the 1986 "Annual Book of ASTM Standards", Section 04.08, Soil
and Rock; Building Stones, 1916 Race STreet, Philadelphia,
Pennsylvania, 19103, which is hereby incorporated by reference into
this rule, and does not include later amendments to, or editions of,
the incorporated material.

5.A.(6)(h) The methods and procedures for determining
slopes outl ined in the "Design of Small Dams", United States
Department of the Interior, Bureau of Reclamation, Second Edition,
1973, 1977 revised reprint, U.S. Government Printing Office,
Washington, D.C., 20402, which is hereby incorporated by reference
into this rule, and does not include later amendments to, or editions
of, the incorporated material, are acceptable for dams up to 50 feet
high. For dams over 50 feet, stability analyses shall be conducted.

5.A.(6)(i) For earth dams, the minimum static stability
factor of safety (FS) under steady state conditions is 1.5, the
minimum FS for rapid drawdown is 1.2, and the minimum FS for dams
requiring residual soil strength analysis shall be determined by the
State Engineer.

5.A.(6)(j) For earth dams the seismic stability criteria
shall be as follows:

5.A.(6)(j)(I) All Class I dams and Large and
Intermediate size Class II dams shall be designed to at least with-
stand the predicted earthquake loads, based upon an analysis of the
potentially active faults, unless sufficient investigations indicate
the faults are not active. Accelerations shall be determined by
methods acceptable to the State Engineer.

5.A.(6)(j)(II) For all Class I dams, and Large and
intermediate size Class II dams, the minimum seismic stability
analysis required shall be a pseudo-static analysis which utilizes an

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