Natural Resources, Water Rights

Section R655-11-5A

Geological and Seismic Study

Notice of Proposed Rule

(Amendment)

DAR File No.: 36507
Filed: 07/18/2012 08:13:33 AM

RULE ANALYSIS

Purpose of the rule or reason for the change:

The current rule requires clarification and update to current industry practice.

Summary of the rule or change:

The current rule requires clarification and update to current industry practice. The statutory obligation continues and there is a continuing need for the rules to provide guidance for requirements for the design, construction, and abandonment of dams.

State statutory or constitutional authorization for this rule:

• Section 73-5a-203

Anticipated cost or savings to:

the state budget:

No cost involved--Clarification of processing does not require a dollar figure.

local governments:

No cost involved--Clarification of processing does not require a dollar figure.

small businesses:

No cost involved--Clarification of processing does not require a dollar figure.

persons other than small businesses, businesses, or local governmental entities:

No cost involved--Clarification of processing does not require a dollar figure.

Compliance costs for affected persons:

No cost involved--Clarification of processing does not require a dollar figure.

Comments by the department head on the fiscal impact the rule may have on businesses:

No physical impact--Clarification of process procedures does not require a dollar figure.

Michael Styler, Executive Director

The full text of this rule may be inspected, during regular business hours, at the Division of Administrative Rules, or at:

Natural Resources
Water RightsRoom 220
1594 W NORTH TEMPLE
SALT LAKE CITY, UT 84116-3154

Direct questions regarding this rule to:

• Marianne Burbidge at the above address, by phone at 801-538-7370, by FAX at 801-538-7467, or by Internet E-mail at marianneburbidge@utah.gov

Interested persons may present their views on this rule by submitting written comments to the address above no later than 5:00 p.m. on:

09/15/2012

This rule may become effective on:

10/22/2012

Authorized by:

Michael Styler, Executive Director

R655. Natural Resources, Water Rights.

R655-11. Requirements for the Design, Construction and Abandonment of Dams.

R655-11-5A. Geological and Seismic Study.

A review of the seismic or earthquake history of the region will be performed to establish the relationship of the site to known faults and epicenters. This will be based primarily on review of existing maps and technical literature and should include major earthquakes during historic time, epicenter locations and magnitudes, and the location of any major or regional fault traces. Geologic conditions at or near the dam site that might indicate recent fault or seismic activity should be included. Resulting design earthquakes and associated site ground motion parameters will be selected considering all available evidence including tectonic and seismological history. The ground motion parameters to be selected for the site will consist of those that are needed by the analyses that are appropriately selected for design and may include peak accelerations, velocities, displacements, response spectra, and acceleration time histories. Both the Maximum Credible Earthquake (MCE) and the Operating Basis Earthquake (OBE) will need to be investigated for all projects. The MCE should be evaluated from the following analyses:

1. A deterministic analysis from active faults in the region surrounding the dam will be performed to estimate magnitude and ground motion parameters. High and moderate hazard dams will be evaluated using ground motion parameters that are at least equal to mean plus 1 standard deviation predictions (84th percentile). At the discretion of the State Engineer, these values may be reduced to mean (50th percentile) for moderate hazard dams. Low hazard dams will be evaluated using ground motion parameters that are at least equal to mean (50th percentile) predictions. Magnitude estimates will consider the potential for multi-segment rupture for segmented faults.

2. [Unless otherwise required by the State Engineer, the random or background event will consist of a minimum magnitude 6.5 event having a peak horizontal site acceleration obtained from a map, herein incorporated by reference, produced by the USGS and entitled "Peak Accelerations (%g) with 5,000 Year Return Time; no fault-specific sources." Alternatively,]A probabilistic analysis will be performed. The most recent United States Geological Survey (USGS) Interactive Deaggregation tool found on the USGS website, using a 5,000 year return interval, can be used to identify magnitude and peak ground motions. [s]Site specific evaluations may be performed to define ground motions for this event if the methods used and assumptions made are acceptable to the State Engineer. Unless waived by the State Engineer, the minimum earthquake magnitude shall be 6.5. At the discretion of the State Engineer, the OBE requirement may be waived.

3. The OBE will be determined by probabilistic methods acceptable to the State Engineer and may include the use of the Deaggregation tool on the USGS website with a 200 year return interval.

 

KEY: dams, earthquakes, floods, reservoirs

Date of Enactment or Last Substantive Amendment: [September 12, 2011]2012

Notice of Continuation: April 14, 2011

Authorizing, and Interpreted or Implemented Law: 73-5a