ML090960682
| ML090960682 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 03/26/2009 |
| From: | Fenster D, Holtz H Bechtel Power Corp, Florida Power & Light Co |
| To: | Office of New Reactors |
| Nguyen C NRO/DNRL 301-415-1177 | |
| References | |
| Download: ML090960682 (21) | |
Text
KARST INVESTIGATION AND CHARACTERIZATION David Fenster Engineering Geology Group Supervisor Bechtel Power Corporation March 26, 2009 William J. Holtz Geologist Bechtel Power Corporation
2 The information provided in the following presentation is of a preliminary nature and is considered DRAFT
3 OUTLINE Review of site stratigraphy Preliminary conclusions based on geologic/geotechnical site investigation Integrated geophysical investigation Conclusions
4 REGIONAL GEOLOGY
5 SITE VICINITY GEOLOGY & STRUCTURE
6 SITE STRATIGRAPHIC COLUMN
7 FLORIDA GEOLOGICAL SURVEY SINKHOLE MAP
8 SITE SPECIFIC DISSOLUTION ISSUES The Florida Geological Survey (FGS) map & report (1985)
- Limestones underlying southeastern Florida have few sinkholes
- Limestones exhibit shallow surface erosion depressions
- Dissolution develops gradually, not catastrophically The FGS Sinkhole Website does not list any occurrence of sinkholes in Dade County through February 2008 The FSAR & SER for Turkey Point Units 3 & 4, and an engineering report (1976) on the Units 3 & 4 foundation and a site to the south:
- Underlying limestones are not grossly cavernous and are no danger to overlying foundations.
- Technical basis: good core recovery, examination of core samples and rock exposures in excavations, absence of karst topographic features, underwater reconnaissance of deep excavations during construction.
9 DISSOLUTION INVESTIGATION Field reconnaissance identified shallow surface depressions.
Borings did not indicate significant dissolution features
- Good core recovery: 60 to 80 percent
- No significant rod drops occurred during drilling
- No unusual loss of drilling fluid
- Caliper logs did not indicate any large voids
- Acoustic logs did not indicate any large voids Geophysical Investigation was conducted to characterize potential dissolution features at the site and to confirm the absence of large dissolution cavities.
10 GEOPHYSICAL SURVEY OVERVIEW Objective: to assess the potential for karst features at the Turkey Point Units 6 & 7 site Geophysical measurements performed by Technos Inc. between January 5 to January 30, 2009
11 GEOPHYSICAL SURVEY OVERVIEW
12 GEOPHYSICAL METHODS UTILIZED Microgravity: A geophysical method in which the acceleration of gravity is measured at points along a survey line or within a survey grid.
Multi-channel Analysis of Surface Waves (MASW): A seismic method that uses the dispersive characteristics of seismic surface waves to calculate the shear-wave velocity of subsurface strata.
Seismic Refraction: A seismic method in which the first-arriving energy from a seismic source is used to calculate the P-Wave velocity of subsurface strata.
13 MICROGRAVITY
14 MASW
15 SEISMIC REFRACTION
16 GEOPHYSICAL SURVEY RESULTS
17
18 GEOPHYSICAL SURVEY RESULTS
19
20 CONCLUSIONS There is no evidence for large paleosinkholes or open voids within the survey area.
Surficial dissolution processes are confined to the Miami Limestone, which will be removed during construction.
21 REFERENCES Florida Geological Survey, Sinkholes Database, Data and Maps, 2007, Available at http://www.dep.state.fl.us/geology/gisdatamaps/
sinkhole_database.htm, updated March 2008.
Scott, T.M., Campbell, K.M., Rupert, F.R., Arthur, J.D., Green, R.C.,
Means, G.H., Missimer, T.M., Lloyd, J.M., Yon, W.J., and Duncan, J.G, Geologic Map of the State of Florida, Map Series 146, Florida Department of Environmental Protection (FDEP), Florida Geologic Survey (FGS), 2001 (Revised - April 15, 2006 by David Anderson).
Sinclair, W. C., and Stewart, J. W., Sinkhole Type, Development, and Distribution in Florida, Map Series No. 110, United States Geological Survey, 1985.