Or. Admin. R. 690-020-0044

Current through Register Vol. 63, No. 6, June 1, 2024

Section 690-020-0044 - Design Requirements for New Dams or to Increase Dam Height: Instrumentation for Monitoring

Designs must include methods for determining if the Dam is operating properly based on the Hazard Rating of the Dam, and include:

(1) A plan to share monitoring data with the Department;

(2) Staff gage near controls for the Conduit or where they can be easily seen by the Dam owner or operator. The staff gage shall be clearly marked in feet and tenths of feet, and extend to within one foot of the Crest. Markings and numbers on the gage rod shall be of sufficient size to be easily readable from the Crest;

(3) Multiple and easily accessible outlets of all Toe Drains. Toe Drains shall be designed to discharge into locations where flows can be evaluated and monitored. Multiple discharge points are required in order to isolate seepage to various sections of the Dam and Foundation. Discharge points must be located where routine Dam maintenance is not likely to damage the drains;

(a) For High Hazard Dams, drains must have a measuring weir or other device, and a basin for settling drainage Water so that internal erosion can be identified;

(b) Where drainage galleries are provided for concrete Dams, seepage measuring devices should be provided and accessible for making the necessary readings;

(4) Unique Identification. All instrumentation and exterior drains shall be labeled with a unique identifying marker designed for durability and to withstand maintenance activities; and

(5) All High Hazard and, when required by the Engineer of Record or State Engineer, Significant Hazard Dams shall have the following instrumentation:

(a) Monuments that allow measurement of the horizontal and vertical movements of the Dam. Control or benchmark monuments shall be placed in areas not subject to movement;

(b) Piezometers to allow monitoring of the phreatic surface within the Dam or for concrete Dams, to determine uplift pressures. Standpipe piezometers must be installed pursuant to monitoring well standards per OAR 690-240-0525;

(c) Instrumentation to measure strong ground motions for publically owned Dams in locations where the peak ground acceleration in the 0.2 percent Annual Probability of Exceedance earthquake is greater than 0.3g at the ground surface.

Or. Admin. R. 690-020-0044

WRD 2-2015, f. & cert. ef. 3/17/2015; WRD 3-2020, amend filed 06/29/2020, effective 7/1/2020

Statutory/Other Authority: ORS 536.027, 540.488

Statutes/Other Implemented: ORS 540.449, 540.488