REV12246 - Laserfiche WebLink

Home Browse Search

Memo, October 25, 2001 Page 2 of 3 Pages Pazk Dam needs to have a safety factor of 1.5 (Rule 4.05.9(8)), with a seismic factor of 1.2 or higher (Class 1 Dam). This engages the requirement for the seismic studies. In addition to strength pazameters for the "old" fill and foundation materials (not the bedrock) from (vicinity of) borings BD-105 and "new" fills in BD-102, I recommend additional borings and strength pazameters as follows for the reasons indicated: 1) 150 feet NW of BD-102 Chazacterize NW abutment materials 2) 100 feet SW of BD-102 Characterize SW abutment materials 3) 150 feet N and 100 feet east of BD-102 Characterize NW failure slo a materials 4) 400 feet N and 300 feet east of BD-102 Characterize NW failure slo e materials 5) 200 feet N of BD-105 Characterize inslo e foundation materials 6) 100 feet N of BD-101 Characterize inslo a foundation materials 7) 200 feet S of BD-105 Characterize SE abutment materials 8) 100 feet SW of BS-102 Characterize abutment materials 9) 100 feet NE of BS-102 Characterize abutment materials 10) 100 feet NW thence 50 feet SW of BS-104 Characterize abutment materials 11) 100 feet NW thence 50 feet NE of BS-104 Chazacterize abutment materials Objectives of the exploration borings are stated on page 4 of Report. The program conducted partially met the objectives. Subsurface stratigraphy and subsurface conditions in the abutments was not accomplished. (Objective 2). Only two samples from one soil horizon was obtained from the Bruce Pazk Dam (Objective 3)(a representative number of samples aze required from all horizons). Field tests were not performed in the abutment materials (additional borings 1, 2, and 7 through 11). A planned program for boring in the neazby slide area (added borings 3 and 4) was not accomplished for the reasons stated on page 5 of the report. Borings, samples and testing of materials in this area is important to validate, by regression analyses, strength measurements. There is an existing slide near the right abutment of the Bruce Pazk Dam. A slide at the abutment would jeopazdize the integrity of the structure. The seismic program would evaluate the adequacy of a 1.2 seismic pazameter in the engineering stability analyses (the program might-indicate-that a lrigher seismic parameter is-warrantee As Kent suggested, the program should include baseline monitoring at the dam site, at a remote site, and at current panels where conditions are similar to those of the dam site. A hypothesis of seismic impacts would be developed from engineering models, calibrated with actual field measurements of current mining activity. A monitoring program at the dam site would measure if seismic impacts aze within the design thresholds as mining activity approaches the structure. The reservoir and associated dams aze structures within the proposed permit and adjacent azea, thus the requirements of Rule 2.05.6(6) aze engaged. As for the seismic program, subsidence models need to be developed. A program to measure the effects of current mining in azeas similaz in geology and mining activity to the reservoir azea could be used to refine a hypothesis for subsidence activity near the reservoir. A subsidence monitoring program [Rule 2.05.6(6)(c)]