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Enclosure 9: Technical Report TR-HBIP-2002-01, Seismic Hazard Assessment for the Humboldt Bay ISFSI Project. Table 3-2, Page 3-48 to Section 5-5
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{{#Wiki_filter:TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 41 15 01/02/1935 22:40 40 15 06/03/1935 17:08 41 06/03/1936 09:15 40 40 9.6 40 19.8 10/10/1936 01:25 41 02/07/1937 04:41 40 30 07/01/1938 18:13 41 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -125 25.2 -125 15 -124 -125 30 -126 27 -125 24 -125 -125 15 -124 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 0 Geomatrix, 199 5 ML5.5 0 Geomatrix, 1995; CNSS, ML 5.7; ML 5.8 2002; Toppozada and others, 2000 0, 14.8 CNSS, 2002; Geomatrix, ML5.0 1995 0 Ellsworth, 1990 Ma-R 5.9; M5.9 0 Bolt and Miller, 1975 ML5.8 0 Geomatrix, 199 5 ML5.9 0 CNSS, 2002 ML5.0 0 Geomatrix, 1995; CNSS, ML 5.8; M 5.8; 2002; Toppozada and ML5.7 others, 2000 0, 14.8 CNSS, 2002; Geomatrix, ML5.0 1995; 3-48 Magnitude References Geomatrix, 199 5 Geomatrix, 1995; UCB, 2002; Toppozada and others, 2000 UCB, 2002; Geomatrix, 1995 Bakun, 2000; Ellsworth, 1990 Bolt and Miller, 1975 Geomatrix, 1995 UCB, 2002 UCB, 2002; Toppozada and others, 2000; Geomatrix, 1995 UCB, 2002; Geomatrix, 1995; Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 09/12/1938 06:10 40 40 12 10/22/1940 11:00 40 30 12/20/1940 23:40 40 02/09/1941 09:44 4042 40 30 10/03/1941 16:13 40 24 40 32.4 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -124 -124 37 -124 6 -124 -125 24 -125 21.6 -124 48 -125 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 0 CNSS, 2002; Toppozada ML5.5; M 5.5 and others, 2000 0 Geomatrix, 1995 ML5.5 0, 15.8 Bolt and Miller, 1975; ML5.5 Geomatrix, 1995 0 CNSS, 2002; Toppozada ML5.5; M 5.5 and others, 2000 0 CNSS, 2002; Ellsworth, Mo-R 6.6; 1990; Toppozada and ML 6.4; M 6.6; others, 2000 M6.6 0 Geomatrix, 1995 ML6.5 0 CNSS, 2002; Ellsworth, Mo-R 6.4; 1990; Toppozada and ML 6.4; M 6.4; others, 2000 M6.4 0 Geomatrix, 1995 ML6.4 3-49 Magnitude References UCB, 2002; Toppozada and others, 2000 Geomatrix, 1995 Bolt and Miller, 1975; Geomatrix, 1995 UCB, 2002; Toppozada and others, 2000 Bakun, 2000; UCB, 2002; Ellsworth, 1990; Toppozada and others, 2000 Geomatrix, 1995 Bakun, 2000; CNSS, 2002; Ellsworth, 1990 & Toppozada and others, 2000 Geomatrix, 1995 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) l(deg. min.) 10/06/1941 06:59 40 24 01/1211944 15:02 40 18 01/16/1944 02:20 40 18 05/02/1945 19:47 41 12 05/27/1947 20:58 40 24 40 18 09/23/1947 13:53 40 24 40 27 08/18/1948 19:12 40 30 40 22.2 04/01/1951 19:21 40 28.2 40 24 10/08/1951 04:10 40 15 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -125 -124 54 -125 6 -123 30 -124 42 -124 13 -125 12 -125 9 -124 42 -124 19.8 -125 18 -125 -124 30 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 0 CNSS, 2002 ML5.0 0 Geomatrix, 1995; CNSS, ML5.1 2002 0 CNSS, 2002 ML5.1 30.1, 0 Geomatrix, 1995; UCB, ML 5.3; ML 5.0 2002 0 CNSS, 2002 ML5.2 10.0 Geomatrix, 199 5 ML5.2 0 CNSS, 2002 ML5.3 0 Geomatrix, 1995 ML5.3 0 CNSS, 2002 ML5.0 10.4 Geomatrix, 1995 ML5.0 0 CNSS, 2002 ML5.0 0 Geomatrix, 1995 ML5.0 0 Ellsworth, 1990; Toppozada Ma-R 6.0; M 6.0; 3-50 Magnitude References UCB, 2002 Geomatrix, 1995; UCB, 2002 CNSS, 2002 Geomatrix, 1995; UCB, 2002 CNSS, 2002 Geomatrix, 1995 CNSS, 2002 Geomatrix, 1995 CNSS, 2002 Geomatrix, 1995 CNSS, 2002 Geomatrix, 199 5 Bakun, 2000; Ellsworth, 1990; Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 40 21 40 16.8 09/22/1952 11:41 40 12 11/25/1954 11:16 40 16.2 40 28.8 12/21/1954 19:56 40 55.8 40 56.4 40 46.8 10/11/1956 16:48 40 40.2 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-0 1 Longitude (deg. min.) -124 36 -124 48 -124 25.2 -125 37.8 -125 27.6 -12346.8 -123 47.4 -123 52.2 -125 46.2 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude and others, 2000 M6.0 0 Geomatrix, 1995 ML5.9 0 CNSS, 2002 ML5.8 0 CNSS, 2002; Geomatrix, ML5.2 1995 0 CNSS, 2002; Ellsworth, Ma-R 6.5; 1990; Toppozada and ML6.1; M6.5; others, 2000 M6.5 0 Geomatrix, 1995 ML6.0 0 Ellsworth, 1990; Toppozada Ma-R 6.6; M 6.6; and others, 2000 M6.6 17.5 Geomatrix, 1995 ML6.6 0 CNSS, 2002 ML6.5 0 CNSS, 2002; Ellsworth, ML6.0, M6.0, 3-51 Magnitude References Toppozada and others, 2000 Geomatrix, 199 5 CNSS, 2002 CNSS, 2002; Geomatrix, 1995 Bakun, 2000; CNSS, 2002; Ellsworth, 1990; Toppozada and others, 2000 Geomatrix, 1995 Bakun, 2000; Ellsworth, 1990; Toppozada and others, 2000 Geomatrix, 1995 CNSS, 2002 Bakun, 2000 & CNSS, 2002; Ellsworth, Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 40 35.4 07/24/1959 01:23 41 7.8 12/05/1959 08:13 40 18 06/06/1960 01:17 40 49.2 40 52.7 12/27/1960 10:35 41 31.2 04/06/1961 04:04 40 10.8 04/1411962 07:53 40 16.2 0711411962 19:43 40 25.8 08/23/1962 19:29 40 51 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -126 4.8 -125 18 -125 25.2 -124 52.8 -124 30 -125 3 -124 45 -125 19.2 -125 31.2 -124 19.8 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 1990; Toppozada and M6.0 others, 2000 0 Geomatrix, 1995 ML6.0 0 CNSS, 2002; Toppozada ML5.8; M 5.8 and others, 2000; Geomatrix, 1995 0 CNSS, 2002; Geomatrix, ML5.1 1995 0 CNSS, 2000 ML5.7 10.1 Geomatrix, 1995 ML5.7 0, 2.0 CNSS, 2002; Geomatrix, ML5.4 1995 0 CNSS, 2002 ML5.0 0 CNSS, 2002; Geomatrix, ML 5.0; ML 5.4 1995 0 CNSS, 2002 ML5.1 0 Geomatrix, 1995; CNSS, ML5.6, ML 5.2, 3-52 Magnitude References 1990; Toppozada and others, 2000 Geomatrix, 1995 CNSS, 2002 Geomatrix, 1995; Toppozada and others, 2000; CNSS, 2002; Geomatrix, 1995 CNSS, 2002 Geomatrix, 1995 CNSS, 2002; Geomatrix, 1995 CNSS, 2002 CNSS, 2002; Geomatrix, 1995 CNSS, 2002 CNSS, 2002; Geomatrix, 1995; Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 41 51 09/16/1965 04:10 40 30 12/10/1967 12:06 40 30 40 33.6 06/26/1968 01:42 40 13.8 40 21.6 09/13/1970 21:10 40 7.8 02/27/1971 00:31 40 16.2 03/01/1972 09:28 40 40.2 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -124 20 -125 48 -124 42 -124 34.8 -124 16.2 -124 3.6 -1254.8 -124 49.8 -125 15 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 2002; Toppozada and M5.6 others, 2000 0 ML5.6 Bolt and Miller, 1975 0 CNSS, 2002; Geomatrix, ML5.0 1995 0 CNSS, 2002; Toppozada ML5.6; M 5.6 and others, 2000 4.6 Geomatrix, 1995 ML5.0 0 Ellsworth, 1990; CNSS, M5.4; ML5.9 2002 14.4 Geomatrix, 199 5 ML5.7 0 UCB, 2002 ML5.4 0 UCB, 2002 ML5.2 0 UCB, 2002 ML5.2 3-53 Magnitude References Toppozada and others, 2000 Bakun,2000 CNSS, 2002; Geomatrix, 1995 CNSS, 2002; Toppozada and others, 2000 Geomatrix, 1995 Ellsworth, 1990; CNSS, 2002 Geomatrix, 1995 UCB, 2002 UCB, 2002 UCB, 2002 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 06/15/1973 19:18 41 30 08/09/1973 02:18 40 15.6 12/21/1973 19:12 40 37.5 07/03/1974 05:00 40 25.44 40 20.4 07/13/1974 11:09 40 22.3 01/28/1975 13:53 40 24.9 06/07/1975 08:46 40 32.49 (Ferndale) 40 31.68 11/26/1976 11:19 41 17.34 41 14.82 12/03/1978 06:48 40 37.2 02/03/1979 09:58 40 52.15 04/07/1979 06:18 41 8.17 03/03/1980 14:17 40 24.83 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -125 31.8 -124 14 -124 35.8 -125 8.16 -125 12.6 -125 10.92 -125 26.76 -124 16.56 -124 17.88 -125 42.5 -125 37.08 -125 50.8 -124 19.03 -125 2.56 -125 07.39 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 0 UCB, 2002 ML5.0 2.0 CNSS, 2002 mb 5.1 30.0 CNSS, 2002 mb5.2 12 CNSS, 2002 mb5.4 0 UCB, 2002 ML5.1 1.00 CNSS, 2002 mb5.0 10.0 CNSS, 2002 mb5.0 23.6 CNSS, 2002 ML 5.3; Me 5.3; 3.27 Geomatrix, 199 5 ML5.2 15.0, 0 CNSS, 2002; Toppozada Ms 6.8; M 6.8; and others, 2000 15 Geomatrix, 1995 ML6.0 98.47 CNSS, 2002 Mc5.0 23.6 CNSS, 2002 ML5.2 5.00 CNSS, 2002 Mc5.4 11.6 CNSS, 2002 ML5.1 3-54 Magnitude References UCB, 2002 CNSS, 2002 CNSS, 2002 CNSS, 2002 UCB, 2002 CNSS, 2002 CNSS, 2002 UCB, 2002; CNSS, 2002 Geomatrix, 1995 CNSS, 2002; Toppozada and others, 2000 Geomatrix, 1995 CNSS, 2002 UCB, 2002 CNSS, 2002 UCB, 2002 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 11/08/1980 10:27 414.44 (Trinidad) 41 7.2 412.46 41 5.84 11/08/1980 11:20 40 14.8 11/08/1980 22:47 40 39.0 11/08/1980 23:07 40 32.1 11/09/1980 04:09 40 30.06 12/07/1980 02:56 40 54.2 12/24/1980 13:29 41 17.76 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -124 36.60 -124 40.2 -124 36.72 -124 44.35 -12444.5 -125 15.6 -124 47.04 -125 20.58 -126 1.86 -124 44.97 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 15.1 CNSS, 2002 Ms 7.2, Me 6.7, ML6.9 0,6 Ellsworth, 1990; Toppozada Ms 7.2, M7.2, and others, 2000; Eaton, M7.4 1989 21.2 Geomatrix, 199 5 ML 7.0 19.8 Tera Corporation, 1982 ML 7.0 15.0 CNSS, 2002 mb5.0 0 UCB, 2002 ML5.0 15.00 CNSS, 2002 Ms5.0 15.00 CNSS, 2002 ML5.4 15 CNSS, 2002 mb5.0 3.2 CNSS, 2002 ML5.0 3-55 Magnitude References NEIC, 2002; CNSS, 2002; UCB, 2002 Bakun, 2000; Ellsworth, 1990; Toppozada and others, 2000 Geomatrix, 1995 Tera Corporation, 1982 CNSS, 2002 UCB, 2002 CNSS, 2002 UCB, 2002 CNSS, 2002 UCB, 2002 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 02/06/1982 12:02 41 04.30 05/29/1983 06:55 40 27.4 08/24/1983 13:36 40 22.39 40 22.8 40 21.3 12/20/1983 10:41 40 25.10 40 20.16 02/28/1984 15:16 40 25.59 02/11/1986 01:15 41 38.04 11/21/1986 23:33 40 22.39 11/21/1986 23:34 40 21.62 40 21.66 07/31/1987 23:56 40 24.97 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -125 08.58 -125 26.64 -124 55.36 -124 49.8 -124 51.9 -125 47.56 -125 33.54 -125 16.53 -125 21.18 -124 37.77 -124 23.72 -124 25.68 -124 23.02 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 9.2 CNSS, 2002 ML5.2 10.0 CNSS, 2002 ML5.4; mb 5.1 11.9 CNSS, 2002 ML5.5 0 Toppozada and others, 2000 M5.6 7.87 Geomatrix, 1995 ML5.6 9.5 CNSS, 2002 ML5.6 10.0 Geomatrix, 1995 ML5.8 4.0 CNSS, 2002 ML5.2 10.0 CNSS, 2002 mb5.0 0.36 CNSS, 2002 ML5.1, M5.2 16.0 CNSS, 2002 ML5.1 7.51 Geomatrix, 1995 ML5.9 17.5 CNSS, 2002 M8 6.0; ML5.6 3-56 Magnitude References UCB, 2002 UCB, 2002; CNSS, 2002 UCB, 2002 Toppozada and others, 2000 Geomatrix, 1995 UCB, 2002 Geomatrix, 1995 UCB, 2002 CNSS, 2002 UCB, 2002; Bakun, 2000 UCB, 2002 Geomatrix, 1995 NEIC, 2002; UCB, 2002 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11,2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 40 25.2 40 25.5 01116/1990 20:08 40 14.05 01/18/1990 11:45 41 11.04 41 11.04 08/16/1991 22:26 41 41.82 41 37.98 08/17/1991 19:29 40 16.90 (Honeydew) 40 17.23 08/17/1991 22:17 41 49.26 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -124 24.6 -124 23.04 -124 18.69 -123 46.08 -123 46.2 -125 23.10 -125 51.66 -124 14.64 -124 14.28 -125 23.82 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 0 NEIC, 2002; Toppozada and Ms6.0; M 6.0 others, 2000 7.2 Geomatrix, 1995 ML5.9 13.0 CNSS, 2002 ML5.4 39.9 UCB, 2002 ML5.2 1.58 Geomatrix, 1995 ML5.2 10.0 CNSS, 2002 Ms 6.3; ML 6.0; mb 5.5 0 Toppozada and others, 2000 M6.3 9.6 CNSS, 2002 ML 6.0; Ms 6.2 0 Toppozada and others, 2000 M6.2 13.5 CNSS, 2002 Ms 7.1, ML6.4, 3-57 Magnitude References NEIC, 2002 & Bakun, 2000; Toppozada and others, 2000 Geomatrix, 1995 UCB, 2002 UCB, 2002 Geomatrix, 1995 NEIC, 2002; UCB, 2002; CNSS, 2002 Toppozada and others, 2000 UCB, 2002; NEIC, 2002 Toppozada and others, 2000 Bakun, 2000; NEIC, 2002; UCB, 2000; Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 41 42.6 41 36.6 03/08/1992 03:43 40 15.35 04/25/1992 18:06 40 19.94 (Petrolia) 40 19.96 40 20.03 04/26/1992 07:41 40 26.13 40 25.86 40 25.63 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -125 37.8 -12530.6 -124 13.98 -124 13.69 -124 13.77 -124 13.78 -124 34.43 -124 34.00 -124 35.79 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References 0 Toppozada and others, §Magnitude mb6.2 2000; Bakun, 2000 M7.0,M7.0 4 Geomatrix, 1995 ML 7.2 11.1 CNSS, 2002 ML5.2 10.6 Oppenheimer and others, Ms7.1 1993 0 M7.2 Toppozada and others, 2000 10.3 mB6.3 CNSS, 2002 19.3 Oppenheimer and others, Ms6.6 1993 19.5 ML6.5 CNSS, 2000 0 M6.6 Toppozada and others, 2000 3-58 Magnitude References CNSS, 2002 Toppozada and others, 2000; Bakun, 2000 Geomatrix, 1995 UCB, 2002 Oppenheimer and others, 1993 Toppozada and others, 2000 UCB, 2002 NEIC, 2002 UCB, 2002, CNSS, 2002 Toppozada and others, 2000 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11,2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Date (GMT) (deg. min.) 04/26/1992 11:18 40 23.38 40 25.03 40 22.51 09/01/1994 15:15 40 24.12 40 26.7 40 24 12/26/1994 14:10 40 44.30 02/19/1995 04:03 40 33.36 01/22/1997 07:17 40 16.32 40 15.42 10/04/1997 10:57 41 03.0 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Longitude (deg. min.) -124 34.30 -124 49.92 -124 35.12 -125 40.8 -125 53.8 -12540.8 -124 18.28 -125 32.34 -124 23.64 -124 29.22 -125 21.72 Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References §Magnitude 21.7 Oppenheimer and others, M8 6.6 1993 14.2 ML6.4; ML6.6 CNSS, 2000 M6.6 0 Toppozada and others, 2000 10.1 CNSS, 2002 M 7.0, mb 6.6, ML 7.0 21.3 UCB, 2002 Mw6.9 0 Toppozada and others, 2000 M7.0 23.5 CNSS, 2000 Mw5.4; M 5.4 10.0 CNSS, 2002 Ms 6.8; ML 6.3 0 Toppozada and others, 2000 M5.6 CNSS, 2002 Mw5.6 7.3 USGSb, 2002 ML5.1; Mw 5.6; Mw5.5 3-59 Magnitude References NEIC, 2002 UCB, 2000; CNSS, 2002 Toppozada and others, 2000 Bakun, 2000; NEIC, 2002; CNSS, 2002 UCB, 2002 Toppozada and others, 2000 UCB, 2000; Dengler and others, 1995 CNSS, 2002; UCB, 2000 Toppozada and others, 2000 CNSS, 2002 UCB, 2002; CNSS, 2002; UCB, 2002 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

TABLE3-2 MAGNITUDE 5 AND LARGER EARTHQUAKES WITHIN 160 KILOMETERS (100 MILES) OF THE HB-ISFSI SITE, 1850 THROUGH APRIL 2002 Origin Time Latitude Longitude Date (GMT) (deg. min.) (deg. min.) 10/26/1997 10:44 41 00.13 -125 09.85 11/26/1998 19:49 40 37.43 -122 24.39 11/27/1998 00:43 40 39.80 -125 18.68 40 40.02 -125 23.04 03/16/2000 15:19 40 22.96 -125 16.23 01/13/2001 13:08 40 44.39 -125 17.06 Notes: Pacific Gas and Electric Company Humboldt Bay ISFSI

Depth (km)

Location References 5.7 CNSS, 2002 23.4 CNSS, 2002 5.4 CNSS, 2000 0 Toppozada and others, 2000 §Magnitude ML5.2 ML5.2 ML5.5 M5.6 5.1 CNSS, 2002 ML 5.8; Me 4.8 5.6 CNSS, 2002 ML5.2 Magnitude References UCB, 2002 UCB, 2002 UCB, 2002 Toppozada and others, 2000 UCB, 2000; CNSS, 2002 CNSS, 2002 Earthquakes from this table are shown on Figure 3-13, except the 1700 Cascadia and 18 Apri11906 San Francisco earthquakes. When more than one location or magnitude is given, the first one listed is used in the figure.

Zero (0) depths are depths that have not been calculated.

§Magnitude symbol explanations: Mb Body wave magnitude Me Coda magnitude Ma-R Gutenberg and Richter magnitude ML Richter local magnitude Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 3-60 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

Ms 20-second surface-wave magnitude Mw Magnitude generally from moment tensor computation. M Moment magnitude (Hanks and Kanamori, 1979) (MI) Pre-instrument (before 1900) intensity magnitude from Toppozada and others (1981) estimated from the size of the areas shaken at various levels of intensity. [MI] Pre-instrumental (before about 1935) intensity magnitude from Bakun (2000), calibrated to equal moment magnitude. {MI} Pre-instrumental (before about 1935) intensity magnitudes from Geomatrix (1995), calibrated to local magnitudes, are from the Decade ofNorth America catalog (DNAG) as described in (Engdahl and Reinhart, 1991) (ML) Pre-instrumental (pre-1900) local magnitude estimate reported by Dengler and others (1992a). [ML] Local magnitude estimated using intensity data and instrumentally determined ground motion amplitudes, as described in Toppozada and others (1978). M Summary magnitude from Ellsworth (1990). The summary magnitude characterizes the relative size of all events listed on his table of major California and Nevada earthquakes, 1769-1989. When choices are available, summary magnitudes are weighted toward long-period estimates of magnitude (e.g., reliable Ms and MG-R). M Magnitudes from Toppozada and others (2000). Magnitude types not specified. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 3-61 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11,2002

EQ Number &Name 1 Ferndale 2 Trinidad TABLE3-3 EARTHQUAKES THAT PRODUCED GROUND MOTIONS GREATER THAN 10°/og AT HUMBOLDT BAY POWER PLANT, 1975 THROUGH 1994 Date Origin Time (GMT) 07 June 1975 846 08 November 1027 1980 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Distance (km)/ Direction from HBPP 221 ssw 50/ NW Pacific Gas and Electric Company Humboldt Bay ISFSI (Source parameters from Table 3-2) Latitude Longitude Magnitude (deg min) (deg min) 40N 32.41 124W 16.56 ML 5.3 41N 4.44 124W 36.60 Ms 7.2 3-62 Depth (km) 23.6 15.1 Free-Field Ground Effects at HBPP Accelerations Recorded at HBPP** 0.03g vert. Units 1 & 2 tripped. Unit 3 0.30g e/w relay tripped; Unit 3 down 0.18g n/s (1) for refueling (1 ). Choppy waves in spent fuel pond, 9" -12" high (1 ). Btrong-motion duration a few seconds (1). No damage (1). 0.076g vert. No structural damage (3). 0.495g e/w Tools fell from storage 0.143g n/s (2,4) rack, glassware broke, separation of paint over previous surface cracks in concrete walls (3). Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

EQ Number &Name 3 Petrolia main shock 4 Petrolia aftershock TABLE3-3 EARTHQUAKES THAT PRODUCED GROUND MOTIONS GREATER THAN 10°/og AT HUMBOLDT BAY POWER PLANT, 1975 THROUGH 1994 Date Origin Time (GMT) 25 April 1992 1806 26 April 1992 0741 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Distance (km)/ Direction from HBPP 55/ s 55/ sw Pacific Gas and Electric Company Humboldt Bay ISFSI (Source parameters from Table 3-2) Latitude Longitude Magnitude (deg min) (deg min) 40N 19.94 124W 13.69 Ms 7.1 40N 26.13 124W 34.43 Ms6.6 3-63 Depth (km) 10.6 19.3 Free-Field Ground Effects at HBPP Accelerations Recorded at HBPP** 0.05g vert. No structural damage 0.22g e/w (5,7,8). Unit 2 offline. 0.22g n/s (6) Water splashed out of spent fuel pond ( 6). New hairline cracks in walls of refueling building, caisson access shaft, and grouted areas near top of spent fuel pond (7). Cracks and leaks in water line to Unit 2 (7). 0.052g vert. No Damage (7). Additional 0.25g e/w electrical problems to fuse 0.23g n/s (6). parts (6). Section 3.0 Regional Geology and Seismicity Rev. 0. September 11,2002

EQ Number &Name 5 Petrolia aftershock 6 TABLE3-3 EARTHQUAKES THAT PRODUCED GROUND MOTIONS GREATER THAN 10°/og AT HUMBOLDT BAY POWER PLANT, 1975 THROUGH 1994 Pacific Gas and Electric Company Humboldt Bay ISFSI (Source parameters from Table 3-2) Free-Field Date Origin Time Distance Latitude Longitude Magnitude Depth Ground Effects at HBPP (GMT) (km)/ (deg min) (deg min) (km) Accelerations Direction Recorded at from HBPP HBPP** 26 April 1992 1118 70/ 40N 23.38 124W 34.30 Ms 6.6 21.7 0.031g vert. No damage (6). sw 0.13g e/w 0.10gnls (6). 26 December 1410 8/ 40N 44.30 124W 18.28 Mw5.4 23.5 0.17g vert.

Strongly felt (1 0). Unit 2 1994 w

0.48g e/w was offline. Unit 1 tripped 0.55g n!s (1 0). offline from quake relay CSMIP response (9). Fuses of recorded 0.41g startup transformer fell (9). to 0.56g in Leak in Unit 1 stem air drip Eureka area tank condensate return line (10). to main condenser (9).

See Table 3-2 for explanation of magnitude symbols.

Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 3-64 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

- Component orientation: vert.= vertical; n/s= horizontal, oriented plant north-south; e/w= horizontal, oriented plant e/w.

(1) Bechtel Power Corporation, 1975 (2) Terra Technology Services, 1980 (3) Nuclear Regulatory Commission, 1980 (4) Pacific Gas and Electric Company, 1984 (5) Nuclear Regulatory Commission, 1992 (6) Pacific Gas and Electric Company, 1992a (7) Pacific Gas and Electric Company, 1992b (8) Pacific Gas and Electric Company, 1992c (9) Pacific Gas and Electric Company, 1994 (10) Pacific Gas and Electric Company, 1995 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 3-65 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11,2002

PACIFIC PLATE Figure 3-1 Generalized regional geologic map showing principal faults and folds, area of active Mendocino uplift (stippled pattern), and major plates (after McLaughlin and others, 2000). Cross section A-A' is shown on Figure 3-2. Details of faulting in the vicinity of Humboldt Bay area shown on Figures 3-3 and 3-7. EXPLANATION QTw Late Cenozoic (Neogene) overlap deposits cr Coast Ranges terrane kr King Range terrane co"m{ Belt fc False Cape terrane Yager terrane cb Central Belt yb Yolla Bolly terrane pp Pickett Peak terrane wl..1 Western Klamath terrane ret Rattlesnake Creek terrane wht Western Hayfork terrane eht Eastern Hayfork terrane Area of active Mendocino uplift Figure 3-1 Humboldt Bay ISFSI Project rrr\\~ Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September II, 2002

E ~ ..c ....... c.. Q.) 0 A Cooskie Fault Zone -10 -20 -26 0 10 Mendocino Uplift Honeydew Petrolia Fault Zone Fault Zone 20 0 00 0 0 30 Bear River Fault Zone Distance {km) 40 I Basin A 1 EeiR1ver ~ Russ ~~~~t~~:on 5 E ..c 0 c.. Gorda Plate 10 Q.) 0~ 0 0 0 0 15 5 mi 50 60 I 8km Notes: Focal mechanisms are depicted as spheres viewed from the southeast; black sectors are tensional, white sectors compressional. Location data and focal mechanisms from M. Magee, Stanford University/USGS (1994). Figure 3-2 Generalized regional structure section A-A' showing depth disttibution of epicenters (open circles) and selected focal mechanisms (beach balls) of earthquakes from M. Magee (Stanford University and USGS), 1994 (after McLaughlin and others. 2000). The location of cross section A-A' is shown on Figure 3-1. Figure 3-2 m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

j PAC!F!C OCEAN 124' Kf1 40'30' QUATERNARY TERTIARY CRETACEOUS-{ PRE-CRETACEOUS-{ 5.0 Miles EXPLANATION Faults: teeth on upper plate of thrust fault; arrows indicate sense of strike slip; dashed where location uncerta1n; dotted where buried or concealed Anticline Anticline, overturned Syncline B) Location of geologic cross section (Figure 3-4) By ./' Location of McKinleyville trench (Woodward-Clyde Consultants, 1980) COASTAL BELT AND OVERLYING SEDIMENTS ,--;:;-::;----] upper Pleistocene and ~ Holocene a\\luv1um ~ upper Pleistocene fluvial ~terraces ~ middle and upper Pleistocene ~ marine terraces ~ ~~:i~~~~a~e~ 0 ~~,~~~::d~~ents (Hookton Formation and/or Carlotta Formation) [!EJ ~;~~:~~;::~~s~~~~~er Formation) Formation Wildcat Group ADJACENT AREAS ~ upper Pleistocene and/or Holocene dune and beach sand [§!] ~~~~~~eis tocene and Holocene [g!!J upper Pleistocene fluvial terraces ~

~~=~::nd upper Pleistocene marine r-::::-:-1 Pleistocene nonmarine sediments

~ (Carlotta Formation) 1 Tmm 1 upper Tertiary marine sediments (lower Wildcat Group) [!!!] lower to middle Tertiary Coastal Belt Franciscan Complex ~ ~;=~~f:coau: g~~~xBelt ~ ~=t~c;:~~~:~~:r;Jr~~:;ic ?) (South Fork Mountain Schist) Figure 3-3 Geologic map of the Humbolt Bay Region. 10 Kilometers m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

B Southwest ( sea level ) 0 0 1 0 ~ fJl 2 Q) E .~ 05 iii jjJ ~ 0 N ~ LL.. Q) i2 Vertical = Horizontal c

~

00 ~ i2 Qi w Little Salmon Fault System Q) c 0 N ~ LL.. ~ c 0 E ~ cti (f) C5 Q) B ~ LL.. fJl £ en

a; I g

~ Q) ~ <.9 Figure 3-4 Geologic cross section of the Humboldt Bay Region. See Figure 3-3 for description of stratagraphic units. The location of cross section B-B' is shown on Figure 3-3. Mad River Fault Zone ~ ~ ~ ~ LL.. ~ Q) LL.. LL.. I ~ ~ Q) Q) i2 c tl Q ~ ~ Li: B' Northeast 0 (sea level)2 0 II I I 0 Figure 3-4 16,000ft I I I I I 5000 m 10 12 14 16 m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

Pliocene 5 Miocene C(

23 c: :(

~ 2::38 C( w I-Eocene 54 Paleocene 65--+---~----------------~ CRETACEOUS TO MIDDLE JURASSIC mya*= million years ago (/) (/) w z- ~~ u2 -C) ~6 0 LO <.0 M 0 0 <.0 ? Hookton Formation (in this report) Carlotta Formation Scotia Bluffs Formation Rio Dell Formation Eel River Formation Pullen Formation Yager Terrane } Wildcat Group Coastal Belt Central Belt r--1 I I Falor ? ? Formation U (Mad River Valley) X C) 0.. E 0 u c co u (/') '(J c co U: Figure 3-5 Composite stratigraphic column, onshore Eel River basin {after Clarke, 1992). Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

\\ \\ \\ \\ \\ ~' ~ _-- $-E:ureka " -- --"nlict* '11e EXPLANATION Faults: teeth on upper plate of thrust fault; arrows indicate sense of strike slip; dashed where location uncertain; dotted where buried or concealed Anticline Anticline, overturned Syncline Terrace Isotope Approximate Name Stage Age (x 1 000 yrs.) Patricks Point 4a 64 Savage Creek Sa 83 McKinleyville Sb 96 Westhaven Sc 103 Fox Farm Sd 120 Sky Horse Se 130 A-Line 7a? 176 Older and much older Terraces 200+ 0 l 3 mi I I I I I 0 5 km Figure 3-6 Marine terrace map of the Humboldt Bay region. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

.*7!. Swiss Hall site Witter ana

others, 2002

. /, tc Fault (projected surface trace) 0 2000 4000 ft 0 500 1000 m Figure 3-7 Surface traces of the Little Salmon fault zone south of the ISFSI site. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-0 1 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

U') Vi 0 0 ~ Vi A -Humboldt Bay _..? - -? ~ - / / / ~ I q_/ A' MSL -200 -400 -600 -1000 ... *:':. :... '.. :. -*~'(-*..,_=_-_--1~ .. **.. :.'. ~ ....,~,~ \\(~?)C~

- I....

Ur" ',;_;..;;;:.-

~. -

~~~*.*~

.. ~,~***-*~:~*~*~***
**~*~M~*-~

" ~,*~.:~ .. :~.-~.*~*~* ~~~-

~-~~~-~======:-~-------------L-1200 Note: Location of cross section shown on Figure 4-1.

0 0 100 200 25 50 400 600ft 100 150 200m Figure 3-8 Cross section A:.A' across the Little Salmon fault zone at Humboldt Hill (after Woodward-Clyde Consultants, 1980, Figure C-15). m Humboldt Bay ISFSI Project Technical Report & TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

r:: t w

0

S:\\51 00s\\5117\\5117.009\\task_13\\02_0715_s3\\_fig_03-09(75).ai EXPLANATION I Qa12l ALLUVIUM 2-OLDER FAN DEPOSITS ~ ALLUVIUM 1-FLUVIAL OR OLD BAY DEPOSITS I Qtm zl MARINE TERRACE DEPOSITS - 2 @ CONVENTIONAL 14C AGE OF 27,730 +/- 170 YEARS BP 0 I 0 100 Feet I I 30 Meters Scale vertical = horizontal Figure 3-9 Geologic cross section A-A' across a trace of the Little Salmon fault zone at College of the Redwoods, 5 kilometers south of Humboldt Bay ISFSI site (after LACO Associates, 1999b, Figure 5). Location of cross section shown on Figure 3-7. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

EXPLANATION ~ ALLUVIUM 5-ACTIVE CHANNEL DEPOSITS ~ ALLUVIUM 2-OLDER FAN DEPOSITS ~ ALLUVIUM 1-FLUVIAL OR OLD BAY DEPOSITS ~ UNDIFFERENTIATED LANDSLIDE DEPOSITS ~ MARINE TERRACE DEPOSITS Figure 3-10 Geologic cross section B-B' across a trace of the Little Salmon fault zone at College of the Redwoods, 5 kilometers south of Humboldt Bay ISFSI site {after LACO Associates, 1999b. Figure 6). Location of cross section shown on Figure 3-7. 0 100 Feet 0 30 Meters Scale vertical = horizontal Figure 3-10 m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0. September 11, 2002

EXPLANATION 1:.15hrDrA:l.fliiUCII:WSI'tw.Cs:rr:not< """'ID!Ni:"-A:'!Cto...I.W.e'"..oors=.J;"'(LIC0':}14t\\J(.Itl~lft,I"J) ('m' ~e I'! 'IC'tl'lt:D IT n>Of:"ll D:::A'M:Y.H) ~ ALLUVIUM 5-ACTIVE CHANNEL DEPOSITS ~ MARINE-BAY MARGIN DEPOSITS 0 I 0 100 Feet I I 30 Meters ~ ALLUVIUM 2-OLDER FAN DEPOSITS ~ ALLUVIUM 1-FLUVIAL OR OLD BAY DEPOSITS ~ MARINE TERRACE DEPOSITS-3 Scale vertical =- horizontal CONVENTIONAL 14C AGE OF 5198

349 YEARS BP Figure 3-11 Geologic cross section C-C' across a trace of the Little Salmon fault zone at College of the Redwoods, 5 kilometers south of Humboldt Bay ISFSI site (after LACO Associates, 1999b. Figure 7}. Location of cross section shown on Figure 3-7.

Figure 3-11 m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 c* l.. Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

EXPLANATION ~ ALLUVIUM 5-ACTIVE CHANNEL DEPOSITS ~ ALLUVIUM 4-YOUNGER FAN DEPOSITS ~ ALLUVIUM 3 - CHANNEL AND POND ~ ALLUVIUM 2-OLDER FAN DEPOSITS ~ ALLUVIUM 1 - FLUVIAL OR OLD BAY DEPOSITS ~ UNDIFFERENTIATED LANDSLIDE DEPOSITS ~ MARINE TERRACE DEPOSITS ~ HOOKTON FORMATION 3,540 50 YEARS BP (CALIBRATED 14C AGE) 14,380 100 YEARS BP (CALIBRATED 14C AGE) CONVENTIONAL "cAGE OF >45,660 YEARS BP CONVENTIONAL 14C AGE OF >44,540 YEARS BP © CONVENTIONAL 14C AGE OF >46,140 YEARS BP Figure 3-12 Geologic cross section D-D' across a trace of the Little Salmon fault zone at College of the Redwoods, 5 kilometers south of Humboldt Bay ISFSI site (afier LACO Associates, 1999b, Figure 8}. Location of cross section shown on Figure 3-7. 0' I 0 100 Feet 0 30 Meters Figure 3-12 Scale vertical = horizontal I! Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September II, 2002

1.0 Vi 0 0 NORTH AMERICAN PLATE 0 <> D PACIFIC PLATE 122°W Figure 3-13 Magnitude 5 and larger earthquakes for the period 1850 through April 2002 within 160 kilometers (1 00 miles) of the site. Earthquakes are scaled by magnitude and differentiated by time periods. Locations are listed in Table 3-2. Numbered earthquakes are included in Table 3-3. Earthquakes within 25 miles (40 kilometers) of the site are included in Figure 3-16. MAGNITUDES 0 5.0+ 0 6.0+

7.0+

TIME PERIODS D 1850-1909 () 1910-1973 0 1974-2002 m Humboldt Bay ISFSI Project Technical Report & TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

L{") Vi 0 0 ~ c.ii 10' 40' 30' 20' 10' 50' 40' 30' 20' 10' 50' 40' 30' 20' 10' 0 0 0 30' 30' 0 0 0 0 OQ o woo ~ ~ Oo 0 Cbo 0 0 ooOtfP O([b C9ci fj 0 o<;lQ o 0 o O't8 Bo 30' 0 30' Figure 3-14 Magnitude 3 and larger earthquakes from the period 197 4 through April 2002 within 160 kilometers (100 miles) of the site. The locations of cross sections C-C' and D-D' (Figure 3-15) also are shown. Locations of magnitude 5 and larger earthquakes are listed in Table 3-2. MAGNITUDES 0 3.0+ 0 4.0+ 0 5.0+ 0 6.0+ 7.0+ .. Humboldt Bay ISFSI Project ~&~ Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

0 D 10 20 ~ ~

I: 30 1-ll.

LiJ c 40 50 60 0 Shoreline 10 20 ~ 30

.::: i' 40

~ ~ 50 ~ 60 oo 70 0 0 Gorda Plate 80 90 100 0 50 100 150 200 250 DISTANCE (KM) 0 I 0 Little Salmon ISFSI Rupture Zone of Fault Zone ~<r 1992 Petrolia Mad River r-- EQ I r--- Fault Zone Q) ~ a: (.) i;::

u

<<) ll. 0 0 0 0 Gorda Plate 0 0 0 20 40 60 80 100 DISTANCE (KM) 0 I 0 Figure 3-15 Seismic cross sections of magnitude 3 and larger earthquakes from the period 197 4 through April 2002. The locations of cross sections C-C' and D-D' and earthquakes symbol legend are shown on Figure 3-14. The location of the plate interface (dashed line) is based on Figure 3-2 and Geomatrix (1994). 300 30 mi I I 50 km ~ 10 20 ! 30 ~ ll. LiJ 40 c 50 60 D' 0 10 20 30 120 10 mi I I 20 km Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

I:

1-ll. LiJ c

"Cij c.O l.O Vi 0 0

~

<ii 0 5 mi I I I 0 10 km MAGNITUDES TIME PERIODS 0 2.0+ 0 6.0+ 0 3.0+ 0 1850-1909 0 4.0+ 7.0+ <> 1910-1973 0 5.0+ 0 1974-2000 Figure 3-16. Magnitude 2 and larger earthquakes from the period 197 4 through April 2002, within 40 kilometers (25 miles) of the site, and earthquakes of magnitude 5 and larger from 1850 through 1973 within the map boundary. Locations of magnitude 5 and greater earthquakes are listed in Table 3-2. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

E 0 5 10 15 ~ ~ 20 I 1-25 0.. w 0 30 35 40 45 50 0 False Cape Fault Bear River Fault Zone Eel River Syncline Little Salmon Table Bluff Fault Zone Fault Mad River Fault Zone I 0 North American plate - e - - "b-Q - - - - - - - - e - - - - -o- - 0 0 0 10 20 30 40 0 oe 0 0 0 o8S Plate Interface 0 oo o oo o o 0 0 c..o f}ofY o 0 Gorda plate 8 6l 0 ° 8 o 0 o 0 0 0 50 60 70 80 DISTANCE (KM) 0 10 mi 1 20km I I I 0 MAGNITUDES 0 2.0+ 0 3.0+ 0 4.0+ 0 5.0+ 0 6.0+ Figure 3-17 Seismic cross section of magnitude 2 and larger earthquakes from the period 197 4 trough April 2002. The location of cross section E-E' is shown on Figure 3-16. Fault locations are based on Figure 3-4; location of the plate interface (dashed line) is based on Figure 3-2 and Geomatrix (1994). E' 5 10 15 20 -6 I 1-0.. w 0 2530 rJ Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

~ If) 0 0 ~ Ui Humboldt Hill Swiss Hall Site A) View north along Highway 101 with Humboldt Hill in the distance. B) Closer view of the Swiss Hall paleoseismic study site. Photo 3-1 Oblique aerial views looking north along the Humboldt Hill anticline and the Little Salmon fault zone. (Photographs taken july 25, 2000, by W.D. Page). Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 3.0 Regional Geology and Seismicity Rev. 0, September 11, 2002

4.1 INTRODUCTION

Section 4.0 Site Geology Humboldt Bay Power Plant and the ISFSI site lie on the east flank ofBuhne Point, a small headland on the eastern shore of Humboldt Bay (Photos 4-1 a and 4-1 b). The site is underlain by a thick sequence of late Tertiary1 and Quaternary sedimentary rocks capped by a late Pleistocene terrace. Buhne Point, which is situated within the Little Salmon fault zone, has been uplifted and tilted to the northeast by displacement on the fault. The results of mapping, borehole, trenching, and dating studies at and near the site are used in the current study to characterize site geology. Trenches and borehole data developed by Earth Sciences Associates (ESA; 1975, 1977) and Woodward-Clyde Consultants (1980) (Figure 4-1) are used to demonstrate the continuity of strata beneath the Humboldt Bay ISFSI site, and to document the locations of tectonic and nontectonic deformation in the site vicinity. Also analyzed and incorporated are data from two new trenches and borehole data from the recent geotechnical study performed to evaluate liquefaction susceptibility and slope stability at the ISFSI site (Section 7.0). Figure 4-2 is a geologic map that shows the locations of the previous and new trenches and borings near the ISFSI site. Data from these investigations were used to demonstrate the continuity of individual stratigraphic horizons across the site and to identify stratigraphic and structural discontinuities that may indicate active faults near the site. For the current evaluation, the stratigraphic and structural data obtained during the extensive investigations for the Humboldt Bay Power Plant in the late 1970s (Earth Sciences Associates, 1975; 1977; Woodward-Clyde Consultants, 1980) were reexamined, along with the results of subsequent studies that included trenching investigations of the Little Salmon fault for College of the Redwoods (LACO Engineering Consultants, 1997, 1999a, b) and for the U.S. Geological Survey (Carver and Burke, 1988; Clarke and Carver, 1992). Field mapping was conducted in March 2000 at and near the ISFSI site to identify geologic features, such as unstable slopes, deformational zones, soil/weathering profiles, and other 1 The geologic time scale is presented in Table 1-1. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-1 Section 4.0 Site Geology Rev. 0, September 16, 2002

features that may be important to assessing the potential for ground deformation or fault rupture at the ISFSI site. As part of that work, the lithostratigraphy, soil stratigraphy, structure, and slope features associated with the terrace on Buhne Point and the hillslopes along the periphery of the terrace were mapped (Figure 4-2). Topographic profiles were measured, and the deposits and soils exposed in the escarpments on the north and south sides of the uplifted terrace at Buhne Point were described in detail. In August 2000, Geomatrix excavated two new trenches, which have a combined length of75 meters. These trenches, and trenching conducted by Woodward-Clyde Consultants (1980), provided continuous exposure of the near-surface Quaternary deposits at the site (Figure 4-3). Section 4.2 describes the physiographic setting of the ISFSI site. Section 4.3 describes site stratigraphy. Particular attention is paid to the nature of the deposits that underlie the ISFSI site and the soil profiles developed on the Buhne Point terrace. The well-bedded middle to late Pleistocene estuarine and fluvial deposits that underlie the site provide the means for identifying late Quaternary faulting and related deformation. The soils on the terrace surface were used to assess the minimum age of near-surface deposits. Section 4.4 describes faulting related to the Little Salmon fault zone, including the Bay Entrance and Buhne Point fault traces. Because the site is on the hanging wallofthe Buhne Point fault, particular attention was paid to the potential for hanging-wall deformation (secondary faulting, folding, and tilting) related to slip on the Bay Entrance, Buhne Point, and Discharge Canal faults. Section 4.5 addresses the continuity of the middle to late Pleistocene deposits beneath and directly adjacent to the ISFSI site. 4.2 PHYSIOGRAPHIC SETTING The ISFSI site is located on a low hill, referred to in this report as Buhne Point hill, on the eastern side of Humboldt Bay opposite the entrance of the bay (Photo 4-1a). The hill, which has a maximum elevation of about 23 meters, extends east ofBuhne Point for about 480 meters, and is 50 to 180 meters wide (Figure 4-2). The hill, capped by an erosional remnant of an uplifted terrace, is an outlier of Humboldt Hill, a northwest-trending ridge that extends southeast of the site (Photo 4-2). Humboldt Hill is a large fault-ramp anticline situated along the leading edge of the hanging wall of the Little Salmon fault zone. Buhne Point hill, where the ISFSI site is located, is bordered on the north by a coastal bluff that drops off steeply (graded slope of about 1:1) to the shore ofHumboldt Bay. The eastern and southern sides ofthe hill are bordered by a low tidal marsh. The western side of the hill is bordered by the village of King Salmon, which is Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-2 Section 4.0 Site Geology Rev. 0, September 16, 2002

built on fill over tidal marsh and beach deposits that extend more than 500 meters into the bay. The westernmost part of the hill forms Buhne Point. Comparison of historical and modem maps indicates that the present hill is only a remnant of a much larger hill that existed in 1850 when Buhne Point was first described as a navigational aid into the entrance of the bay. The first detailed map of the area, made in 1858 (Figure 4-4), shows a flat-iron-shaped hill having steep bluffs along its northern and southwestern sides. The flat terrace surface slopes gently away from the bluffs to the southeast. The present shoreline is about 400 meters southeast of the 1858 shoreline (Figure 4-4). The dramatic coastal retreat and loss of most of Buhne Point hill to wave erosion began when the entrance to the bay was deepened, and jetties (Photo 4-2) were placed adjacent to the entrance to provide a permanent deep-water access for ships during the late 1800s. The bluff retreat was arrested when riprap was placed along the base of the bluff in the early 1950s to prevent further wave erosion (Photo 4-3). Buhne Point hill was formed by tectonic uplift associated with the Little Salmon fault zone combined with wave erosion. The escarpment along the southwest side of the hill is interpreted to be the eroded fault scarp produced by down-on-the-southwest displacement along the Buhne Point trace of the Little Salmon fault zone. The northeast margin of the hill that is apparent on the 1858 map (Figure 4-4) appears to be related, at least in part, to down-to-the-northeast displacement on a small secondary fault, the Discharge Canal fault. The bluff that existed on the northwest side ofBuhne Point hill in 1858 was the eroded sea cliff that faced the ocean across from the natural entrance to the bay. This bluff has since retreated to its present position at the northern side of the plant area. An approximately east-west topographic profile and geologic cross section along Buhne Point hill parallel to the coast (Figure 4-5) indicates two distinct terrace surfaces along this profile. The higher terrace, the Buhne Point terrace (Qpht on Figure 4-2), is a planar geomorphic surface having a gentle (2 to 4 degrees) southeast tilt (Photo 4-4). The small inset terrace below this surface on the western end of the hill (Figure 4-5) appears to have been man made, because it is not evident on the 185 8 survey map. Also, the strata at the present ground surface are not weathered, indicating that the soils were removed. The surface of the Buhne Point terrace was modified in several places during construction of the power plant. For example, low-angle oblique aerial photographs in PG&E's archives (Photos 4-5a and 4-5b) show grading activities from south of the old security fence to the edge of the bluff Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-3 Section 4.0 Site Geology Rev. 0, September 16, 2002

on the north side of the terrace. Parts of the Buhne Point terrace surface (Qpht on Figure 4-2) in the vicinity of the ISFSI site may have been lowered by as much as 2 to 3 meters; the most significant lowering occurred along the edge of the bluff, decreasing toward the security fence. In several places, the disturbed areas are underlain by about a meter of fill. The ISFSI site is located near the old security fence in the area of disturbed ground. 4.3 STRATIGRAPHY As described in Section 3.2.1, the ISFSI site is underlain by more than 900 meters of late Pliocene and Quaternary deposits. Three lithostratigraphic formations separated by unconformities were encountered at the site, as shown on Figure 4-6. From oldest to youngest, these are the Rio Dell Formation, the Scotia Bluffs Formation and the Hookton Formation, which is divided into lower and upper members. The following descriptions of the Rio Dell, Scotia Bluffs, and lower Hookton formations are based on Woodward-Clyde Consultants (1980). In addition to data from the Woodward-Clyde study, the description of the upper member of the Hookton Formation includes information obtained from geotechnical borings and trenches at the ISFSI site and from surface outcrops in the Buhne Point area. At Buhne Point, a coastal terrace surface is formed in the upper Hookton sediments; this surface appears to be conformable with the upper Hookton sediments. Remnants of a relict paleosol described in Section 4.3.4 are preserved in undisturbed areas on the terrace surface. The characteristics of this paleosol enable correlation with the regional soil chronosequence (Burke and others, 1986; Carver and others, 1986b; Carver and Burke, 1992) and assignment of an age for the terrace. Around Buhne Point hill, the Hookton deposits are unconformably overlain by Holocene colluvial, landslide, alluvial, and estuarine deposits. Extensive areas of the site have been graded, and in most places the natural soils/surface weathering profile have been removed or buried by man-made fill. 4.3.1 Rio Dell Formation (Late Pliocene to Early Pleistocene) The Rio Dell Formation is a homogeneous marine mudstone that is encountered in boreholes at 520 meters beneath the site. The formation is about 600 meters thick. Regionally, the Rio Dell Formation is time-transgressive-marine fossils indicate age ranges from late Pliocene to Pleistocene. Near the site, the uppermost Rio Dell Formation is estimated to be 1.1 +/- 0.2 million years old (Woodward-Clyde Consultants, 1980), making its age early Pleistocene. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-4 Section 4.0 Site Geology Rev. 0, September 16,2002

4.3.2 Scotia Bluffs(?) Formation (Early Pleistocene) At the site, the Rio Dell Formation is unconformably overlain by more than 340 meters of shallow-water sandy marine sediments that probably are correlative with the Scotia Bluffs Formation 2of Ogle (1953). The deposits consist mostly of silty sand and sandy silt interbedded with clayey sediment. The clay beds provide excellent marker horizons that can be recognized on geophysical logs, particularly the natural gamma-ray logs. In the site area, Woodward-Clyde Consultants (1980) subdivided the formation into eight units, labeled 0 though V (from youngest to oldest). The precise age of the Scotia Bluffs(?) Formation has not been determined, but it probably was deposited between about 1.1 million years ago (the estimated age of the upper Rio Del Formation) and about 780,000 years ago (older than the Brunhes/Matuyama magnetic reversal3 that was identified by Woodward-Clyde Consultants [ 1980] from borehole and outcrop samples at Centerville Beach). Therefore, the Scotia Bluffs(?) Formation is early Pleistocene in age. 4.3.3 Hookton Formation (Middle to Late Pleistocene) As described in Section 3.2.1, (the Hookton Formation consists of middle to late Pleistocene interbedded shallow marine, estuarine, and fluvial deposits that unconformably overlie Scotia Bluffs(?) and older formations. In the vicinity ofBuhne Point, the Hookton Formation is divided into a lower and an upper unit (Figures 4-6 and 4-7). The lower Hookton Formation deposits consist of alternating sand, silty sand, gravelly sand, silty clay, and clay about 265 to 27 5 meters thick. The thickness of the Hookton Formation varies near the site because of active faulting and folding during deposition of the unit. For example, deep boreholes and cross sections in Woodward-Clyde Consultants (1980) show that the thickness of the lower Hookton beds increases from the hanging-wall blocks (upthrown sides) to the footwall blocks (downthrown sides) across the Buhne Point, Bay Entrance, and Little Salmon faults, indicating that folding and faulting occurred during deposition of the lower Hookton Formation. In addition, tectonic thickening (i.e., duplication/stacking of stratigraphic section by superposition of older units over younger units by reverse faulting) accounts for apparent stratigraphic thickening near the site. 2 Following the nomenclature used by Woodward-Clyde Consultants (1980), a querry is used after Scotia Bluffs to indicate that correlation of this unit, where it is encountered in borings, to Ogle's (1953) type locality for the Scotia Bluffs Formation is uncertain. The querry is not used on geologic maps, where the deposits are exposed at the surface and the correlation is more reliable. 3 Woodward-Clyde Consultants (1980) used an age of about 700,000 years for the polarity transition between the Matuyama and Brunhes polarity epochs. Based on recent dating using advanced potassium-argon techniques, the date of this transition is now placed at 780,000 years (Baksi and others, 1992). Previously, this boundary was thought to be at 760,000 years (lzett and others, 1988), and before that was placed at 730,000 years (Mankinen and Dalrymple, 1979). Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-5 Section 4.0 Site Geology Rev. 0, September 16, 2002

Laterally persistent clay beds, typically overlain by gravelly sands, provide useful marker horizons. A distinctive clay bed, Unit F, near the top of the lower Hookton Formation is a particularly useful marker horizon that has been identified in borings across the site and in the western end of Trench 11-T6c at the northwest end of Buhne Point. The age of the uppermost part of the lower Hookton Formation is about 160,000 +/- 40,000 years, based on amino acid racemization dates on fossil shell material collected from clayey sediment in a Caltrans road cut near the northern end of Humboldt Hill about 900 meters south of the site (Woodward-Clyde Consultants, 1980). The age of the Unit F clay is estimated to be 310,000 +/- 70,000 years, based on average rates of deposition between the dated clay (top of the lower Hookton Formation) above Unit F and the basal sediments of the Hookton Formation that are estimated to have been deposited between 600,000 +/-1 00,000 years ago (Woodward-Clyde Consultants, 1980). Upper Hookton Formation deposits consist primarily of silt and clay alternating with thinner sand and gravel lenses. No distinctive marker horizons were identified in the upper Hookton Formation that could be correlated across the Little Salmon and Bay Entrance faults, but the deposits are significantly thicker on the downthrown sides of these faults. As exposed in trenches and in the sea cliff along the north side of the Buhne Point terrace, the deposits underlying the terrace commonly contain distinctive layers having sharp contacts (Photo 4-6). The textures of the strata vary somewhat laterally, but individual layers commonly can be traced for several meters. The clayey bay mud deposits tend to be more laterally persistent than the interbedded sandy and silty layers. However, both sandy and clayey marker horizons in the upper Hookton Formation deposits exposed in trenches were traceable across the ISFSI site. Lithologic contacts could be mapped with sufficient resolution to preclude any fault displacements larger than a few centimeters (typically 2 centimeters or less), as shown on the logs of trench walls (Figures 4-8 and 4-9). Correlation of the stratigraphy in boreholes to the strata exposed in the sea cliff and local trenches indicates that the boundary between the lower and upper members of the Hookton Formation is at the base of the very dense sandy gravel 16 to 23 meters below the ISFSI site. Geologic cross sections X-X5 and Y-Y1 (Figures 4-5 and 4-10) depict the position of this contact beneath the site, as well as the correlation of two distinctive estuarine mud units in the upper Hookton Formation. The upper part of the lower Hookton Formation consists of very dense, poorly to well-graded sand and silty sand with occasional gravel overlying the Unit F clay bed, which occurs at a depth of 46 meters in borehole GMX-99-2. The two layers of bay mud (clay and silt) in the upper Hookton Formation are separated by a 9-to 1 0-meter-thick sandy and silty Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-6 Section 4.0 Site Geology Rev. 0, September 16, 2002

deposit, the texture of which ranges laterally from silty sand to low-to high-plasticity silt. These lateral variations are interpreted to be facies changes. Deposits overlying the uppermost clay bed are predominately sandy and silty clay, well to poorly graded sand, and silty and clayey sand. These deposits, as well as the upper part of the highest bay mud clay and silt beds, were exposed in trenches WCC-11-T6a, GMX-T1, and GMX-T2 (Figures 4-3,4-8, and 4-9). A layer of clayey man-made fill overlies the upper Hookton Formation across most of the ISFSI site. The fill ranges from 0 to 3.2 meters thick, but typically is 0.6 to 1 meter thick. 4.3.4 Bohne Point Terrace and Paleosol (Late Pleistocene) The uppermost Hookton deposits are conformable with a planar geomorphic surface, the Buhne Point terrace (Qpht on Figure 4-2), which dips gently (2 to 4 degrees) to the southeast. A strongly developed soil has formed in the near-surface deposits. This paleosol crops out in exposures on the steep slopes northeast and southwest of the ISFSI site, and in the southwest end of trench GMX-T2. Based on these exposures, the paleosol appears to be concordant with the tilted terrace surface. It has a well-developed argillic horizon, reddish brown (7.SYR hue) color, clay films, and strong structure (Figure 4-11 and Table 4-1 ). The presence of a relatively thick, strongly developed argillic horizon (Bt horizon) and the reddish color indicate that the soil on the Buhne Point terrace is correlative with Class II (80,000- and 1 OS,OOO-year-old) soils developed on marine terraces in the Humboldt Bay area (Carver and Burke, 1992). In particular, the degree of soil development on the terrace surface at Buhne Point is similar to the soil at the South Port Landing quarry on Table Bluff, where a thermoluminescence age of 103,000 years was obtained for sediments underlying the terrace (Berger and others, 1991 ). The Buhne Point terrace is interpreted to have formed during a high stand of sea level in the late Pleistocene, most likely during marine oxygen-isotope Stage Sc or Sa. The ages of oxygen-isotope StageS marine terraces along the California coast are well documented (for example, Hanson and others, 1994); Stage Se marine terraces are dated at 120,000 to 12S,OOO years, Stage Sc terraces are approximately 10S,OOO years old, and Stage Sa formed approximately 80,000 years ago. The soils data described above suggest that the terrace has been emergent since at least Stage Sa and possibly longer. This conclusion is consistent with previous estimates of the age of the Buhne Point terrace by Woodward-Clyde Consultants (1980), who interpreted it as post-upper Hookton Formation sediment deposited after deposition of a clay bed containing shell material having a 160,000 +/- 40,000-year-old amino acid racemization age, and prior to 37,000 years ago, as determined from radiocarbon dating of wood samples from Trench 11-T6a. This date is older than the effective range of radiocarbon dating in 1980. A wood sample from upper Hookton deposits collected from trench GMX T2 (Figure 4-9) yielded a radiocarbon age of Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-7 Section 4.0 Site Geology Rev. 0, September 16, 2002

>45,730 radiocarbon years B.P., confirming that the upper Hookton deposits are older than the effective age range for radiocarbon dating ( Geomatrix, 2002e ). The strongly developed soil on the Buhne Point terrace supports an age of more than 80,000 years. 4.3.5 Surficial Deposits (Holocene) Holocene surficial deposits in the Buhne Point area include alluvial/estuarine marsh sediments, colluvium on the slopes, and shallow landslides (Figure 4-2). The alluvial/estuarine deposits underlie the flat area southwest of the Buhne Point terrace in the King Salmon A venue area and east of the Discharge Canal. Colluvium derived from the eroded fault scarp along the southwest side of Buhne Point terrace probably interfingers with the alluvial/estuarine sediments. Small landslides along the bluffs that border the Buhne Point terrace (Figure 4-2) are most abundant on the sea cliff adjacent to Humboldt Bay on the north side of the terrace. Most of the landslides are shallow ( < 2 meters thick), translational landslides. However, the two northwestemmost landslides along the sea cliff appear to be somewhat deeper (5 to 7 meters) and to have rotational movement. This landsliding postdates the grading of the sea cliff and placement ofriprap along the shoreline, which were completed during the late 1950s. No large landslides were observed along the bluff and, based on geologic conditions underlying the bluff, no large, deep-seated landslides are expected. 4.4 FAULTING IN THE SITE VICINITY ASSOCIATED WITH THE LITTLE SALMON FAULT ZONE As described in Section 3.2.2 and shown on Figure 3-7, four traces of the Little Salmon fault zone are mapped in the vicinity of the Humboldt Bay ISFSI site. These include two primary fault traces, the Little Salmon and Bay Entrance faults, and two subsidiary faults in the hanging wall of the Bay Entrance fault, the Buhne Point and Discharge Canal faults. The Little Salmon fault corresponds to the middle trace of the Little Salmon fault zone to the southeast, and the Bay Entrance fault corresponds to the eastern trace of the Little Salmon fault zone to the southeast. The Little Salmon, Bay Entrance, and Buhne Point faults all dip to the northeast and displace the late Pleistocene Hookton Formation down to the southwest (Figures 4-12,4-13, and 4-14). The Discharge Canal fault dips steeply to the southwest and has down-to-the-northeast displacement. 4.4.1 Little Salmon Fault The location of the Little Salmon fault near the site is based on borings and seismic lines conducted by Woodward-Clyde Consultants (1980) (Figure 4-1 ). The fault strikes about N45°W Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-8 Section 4.0 Site Geology Rev. 0, September 16, 2002

and dips about 25°NE (Figure 4-12). The fault projects to the surface about 2.2 kilometers southwest of the ISFSI site. Projection of the structure contours shown on Figure 4-12 to the northwest places the fault about 1,300 meters beneath the western boundary of the Humboldt Bay Power Plant site. However, the fault was not encountered in boring WCC-4 (Figure 4-12), indicating that this trace either dies out south of the site, or its dip steepens at depth, placing the fault more than 1,600 meters below the ISFSI site. In either case, the Little Salmon fault was not encountered in site area borings or trenches. As described in Section 3.2.2, the Little Salmon fault displaces the entire lower Hookton section at the northern end of Humboldt Hill, placing Rio Dell Formation over Hookton sediments (Figure 4-15). It appears that, north of Humboldt Hill, slip on the Little Salmon trace of the Little Salmon fault zone is transferred to the Bay Entrance fault. 4.4.2 Bay Entrance Fault The Bay Entrance fault is the closest of the main traces of the Little Salmon fault zone to the ISFSI site. As inferred from borings, the fault strikes N5-1 0°W and dips approximately 50° to 60°E (Figure 4-13). The fault projects to the surface about 500 meters west of the ISFSI site (Figure 4-16). The closest distance to the fault (fault-normal distance measured to the center of the site) is between about 410 and 4 70 meters. The fault appears to have a right-slip component that is about 50 percent of the dip-slip separation, based on analysis of boring and geophysical data (Woodward-Clyde Consultants, 1980). The base of the Hookton Formation is displaced about 440 meters (dip-slip), and the upper Hookton Formation is displaced about 270 meters (Woodward-Clyde Consultants, 1980, their Figure C-1 0 and Table 2). Progressive separation of the older beds in the Hookton Formation indicates the fault was active during deposition of the Hookton Formation. The long-term, dip-slip displacement rate on the Bay Entrance fault southwest of the ISFSI site is believed to be 1 to 2 millimeters per year. South of the plant site, the Bay Entrance fault corresponds to the east trace of the Little Salmon fault zone (Figure 3-7). In a quarry exposure directly south of College of the Redwoods, this trace displaces lower Wildcat sedimentary rocks (Pullen Formation) over late Pleistocene and Holocene sediments (Carver and Burke, 1988). To the south, at Salmon Creek, this trace deforms a late Holocene alluvial terrace. Based on the displaced terraces, Carver and Burke (1987) estimate the late Holocene slip rate to be 2 to 3 millimeters per year. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-9 Section 4.0 Site Geology Rev. 0, September 16, 2002

4.4.3 Buhne Point Fault The location of the Buhne Point fault is based on analysis of site borings (Figures 4-14 and 4-16). The fault strikes about N45-70°W. The fault dips about 35°NE down to elevation -900 feet (-275 meters), where the dip flattens to less than 20° (Figure 4-16). Below elevation -300 meters (-1,000 feet), the dip of the fault steepens to about 45° and probably continues to steepen until the fault merges with the Bay Entrance fault. The fault plane lies about 140 to 160 meters beneath the ISFSI site. The projected surface trace of the Buhne Point fault is parallel to and southwest of the southwest margin of the Buhne Point terrace, about 180 meters southwest of the ISFSI site (Figure 4-14 ). The 5-to 15-meter-high scarp along the southwest side of the Buhne Point terrace is interpreted to be a wave-eroded fault scarp associated with the Buhne Point fault. Although erosion and grading during plant construction modified the scarp, it reflects the general trend of the surface trace. The Buhne Point fault shows progressively greater vertical separation of older horizons. It displaces the Scotia Bluffs(?) Formation 71 meters (vertical separation on Unit Q); the base of the Hookton Formation 49 meters; and the Unit L clay in the lower part of the Hookton 21 meters (Woodward-Clyde Consultants, 1980, Figure C-8). Structure contours on the top of Unit F in the vicinity of the ISFSI site (Figure 4-17) indicate the vertical displacement on the top of this unit in the upper part of the lower Hookton Formation ranges from 6 to 1 0 meters. The upper Hookton underlying the terrace at Buhne Point is tilted 2 to 4 degrees to the southeast, indicating continued deformation and faulting on the Bay Entrance and Buhne Point faults during the late Pleistocene (the past 80,000 years). Based on the displacement of Unit F (160,000 +/- 40,000 years old), the long-term-average slip rate on the Buhne Point fault (dip slip) is about 0.1 millimeter per year. This slip rate is an order of magnitude lower than the slip rate for the Little Salmon and Bay Entrance traces of the fault zone. Woodward-Clyde Consultants (1980) excavated trenches 11-T6b and 11-T6c across the scarp that borders the Buhne Point terrace (Figures 4-2, 4-18, and 4-19). Both trenches exposed zones of fractures and small-displacement faults in the upper part of the lower Hookton Formation. The fractures and small faults are similar to those observed in the hanging wall of other reverse faults that were investigated during regional fault studies (Woodward-Clyde Consultants, 1980; Carver, 1987b ). For example, Woodward-Clyde Consultants (1980) mapped similar features in the hanging wall of the McKinleyville fault, about 25 kilometers north of the plant site (Figure 4-Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-10 Section 4.0 Site Geology Rev. 0, September 16, 2002

20). The fractures and small-displacement faults are inferred to represent deformation in the hanging wall along the leading edge of a reverse fault, suggesting that a fault lies within a few tens of meters of the present topographic scarp. Based on the structure contours on the top of the Unit F clay (Figure 4-17), a small splay branches from the main trace of the Buhne Point fault to the northwest toward Buhne Point. The vertical displacement on the splay fault is about 3 meters. Interpretation of the structure contour map of the top of the Unit F clay (Figure 4-17) and geologic cross section W-W1 (Figure 4-21) indicate this marker horizon is displaced 6 to 10 meters down on the southwest across the Buhne Point fault. The relatively small displacement on this fault is not enough to account for the total uplift of the Buhne Point terrace, which, at its highest point, is about 20 meters above mean lower low water. Faulting on the Bay Entrance fault must accommodate part of the uplift. 4.4.4 Discharge Canal Fault A small fault, informally referred to as the Discharge Canal fault, displaces the upper Hookton Formation with a vertical separation of three meters or more. The fault is partly exposed in a hand-dug pit in the sea cliff about 75 meters west of the discharge canal for the power plant (outcrop JW-7; Figures 4-2 and 4-22). In this exposure, a sand layer is clearly displaced down on the northeast by numerous closely spaced, steeply dipping to near-vertical (70°S to 90°) faults that generally strike N50°W. The fault is associated with a monoclinal flexure exposed in trenches BP-2 and BP-3, east of the ISFSI site and directly west of the discharge canal (Figure 4-2). Logs of these trenches (Earth Sciences Associates, 1977) show a sand layer in the upper Hookton Formation that is deformed into a steep "monocline" (down on the northeast) that trends N70°W (Figures 4-23 and 4-24). The vertical separation across the feature is greater than or about equal to 3 meters (the limit of the exposure in trench BP-2). The surface trace defined by these exposures corresponds to a 3-meter down-to-the-northeast step in the top of Unit F (Figure 4-17). Based on the location of the offset in Unit F relative to the surface trace, the fault dips 70° to 80° to the southwest. The Discharge Canal fault is interpreted to be a backthrust on the hanging wall of the Buhne Point fault (Figure 4-16). The "monocline" represents either folding above the tip of a blind reverse fault, or hanging-wall deformation above a backthrust that daylights (or is covered by young bay sediments) to the northeast. Another small fault crops out in the sea cliff about 45 meters east of the mapped trace of the Discharge Canal fault (Figure 4-2), where a 10- to 20-centimeter-thick sand layer in the upper Hookton Formation is abruptly truncated by a zone of faint, closely space shears. The fault strikes N32°W and dips 77°SW. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-0 1 4-11 Section 4.0 Site Geology Rev. 0, September 16, 2002

Assuming reverse slip, the displacement exceeds about 1.5 meters (and exceeds the height of the exposure). 4.4.5 Other Minor Faults As shown on Figure 4-2, the only stratigraphic displacements observed near the site were exposed in trench WCC-11-T6a, more than 30 meters west of the ISFSI site, where a small, rootless, graben-shaped feature is located in bedded silts (Appendix 4A, Figure 4A-12, Sheet 3, Station 160m). Two narrow zones of antithetic faults that are spaced about 30 centimeters apart form a depression about 15 centimeters deep in the silt bed; there is no apparent vertical separation across the feature. Woodward-Clyde Consultants (1980) attributes the feature to soft-sediment deformation during deposition of the Hookton sediments, because the underlying and overlying sediments were not similarly disturbed. The bounding shears, however, have characteristics that are similar to the "monocline" exposed in trenches BP-2 and BP-3 and in the sea cliff exposure (Figure 4-2). Therefore, the feature probably represents minor secondary deformation (bending-moment normal faulting) in the hanging-wall block of the Buhne Point fault. As described above, zones of small faults and fractures also are evident in trenches WCC-11-T6b and WCC-11-T6c (Figures 4-2, 4-18, and 4-19). 4.5 CONTINUITY OF STRATA BENEATH THE SITE This section discusses the continuity of the strata beneath the ISFSI site, both the Unit F clay of the upper lower Hookton Formation, and upper Hookton strata. 4.5.1 Unit F Clay (Upper Lower Hookton Formation) The potential for detecting small faults in the Unit F marker horizon is affected by (1) the accuracy of the stratigraphic picks in individual boreholes (typically less than 0.3 to 0.6 meters); (2) the spacing of the boreholes in the site vicinity that penetrate to Unit F (which varies, as shown on Figure 4-17); (3) the possibility of erosional irregularities in the top of Unit F; and ( 4) the possibility of broad folding (non-brittle deformation) of Unit F. Considering these factors, the limit of resolution for detecting faults in Unit F beneath the ISFSI site is estimated to be about 2 meters. Figure 4-17 shows a structure contour map based on the lithologic picks for the elevation of the top of Unit F encountered in site area boreholes and in trench WCC-11-T6c (Geomatrix, 2002a, 2002b ). Unit F is about 40 meters below the ISFSI site, where the contact between Unit F and Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-12 Section 4.0 Site Geology Rev. 0, September 16, 2002

the overlying sand and gravel generally strikes N30-40°E and dips 5°SE. The dip is shallower to the east adjacent to the Discharge Canal fault; southeast of the site, the strike rotates to trend more eastward. This rotation in strike may reflect erosion of the upper contact of Unit F, the presence of a southwest-verging thrust fault at depth, or broad folding of Unit F. The available data indicate that erosion and/or broad synclinal folding probably account for the swing in structure contours, although faulting at depth cannot be ruled out. If a southwest-verging reverse fault was present at depth, its subsurface trace would project to the northeast of the site, and the up-dip projection of the fault plane would be approximately toward the site. However, slip on this hypothetical fault would die out along strike to the northwest, based on the decreased to no deflection in the structure contour at and northeast of the site. As described below, the absence of faulting in near-surface sediments (i.e., strata of the upper Hookton Formation) at and near the ISFSI site is documented in trenches of this and previous studies. For comparison, the deformation of the upper Hookton Formation strata by the Discharge Canal fault is readily identifiable in trenches and test pits. The absence of significant faulting in the trenches indicates that the fault does not exist, does not project through the site, or has not been active for more than 80,000 years. Evidence of erosion on the top of Unit F is indicated in an alignment of five closely spaced boreholes that are from 2.4 to 3.6 meters apart. These boreholes were drilled about 200 meters east-southeast of the ISFSI site as part of a cross-hole shear-wave-velocity experiment (boreholes WCC80-CH-1 through WCC80-CH-5 on Figure 4-17). The lithologic logs for these boreholes indicate 1.5 meters of local relief in the top of the Unit F clay. Figures 4-25a and bare geologic cross sections at the top of Unit F that show two alternative interpretations of the CH series boreholes. As shown, the variability in the elevation of the top of Unit F could be due to either a small fault (Figure 4-25a), or a cut-and-fill channel (Figure 4-25b). If it were a fault, the vertical separation between boreholes WCC80-CH4 and WCC80-CH3 would be between 1.2 and 1.7 meters down to the east. However, given the negligible ( ~0.3 meter) net vertical separation across the series of boreholes, and the anomalous apparent west dip of the top of Unit F between boreholes WCC80-CH3 and WCC80-CH5 compared to the trend of the Unit F surface (Figure 4-17), the relief probably reflects a cut-and-fill channel. Geologic cross section W-W1 (Figure 4-21) trends northeast/southwest, approximately perpendicular to the strike of the northeastern splay of the Buhne Point and the Discharge Canal faults. Unit F can be traced continuously across the uplifted block between these faults, which displace the Unit F clay 6 to 10 meters and 3 to 5 meters (vertical separation), respectively. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-13 Section 4.0 Site Geology Rev. 0, September 16, 2002

There are no discemable faults (faults having a vertical separation greater than 2 meters) in this 31 0,000-year-old clay marker horizon beneath the ISFSI site. 4.5.2 Upper Hookton Strata Geologic cross section Y-Y1 (Figure 4-1 0), which extends north/south through the ISFSI site, illustrates the stratigraphic relations in the upper Hookton deposits beneath the site. Based on the borings and observations made in the sea cliff exposure, the upper Hookton deposits are continuous; there is no evidence these deposits, which are at least 80,000 year old, are faulted beneath the site. Trenches WCC-11-T6a and GMX-T1 cross the ISFSI site in a N75°W direction (see Figures 4-3 and 4-8, Photo 4-7, and Appendix 4A). Trench GMX-T2 crosses the site in a N24-37°E direction, which is approximately perpendicular to the trend of the Buhne Point and Discharge Canal faults (Photo 4-8). These trenches provided continuous exposure in upper Hookton Formation bay mud deposits across the ISFSI site. Trench WCC-11-T6a extended for more than 200 meters along the uplifted block (Buhne Point terrace) that lies between the northeast-dipping Buhne Point fault and the southwest-dipping backthrust near the Discharge Canal (Figure 4-2). The trench exposures provide direct evidence for the absence of faulting beneath the ISFSI site with a high degree of resolution (typically less than 2 centimeters) in the exposed deposits, which are at least 80,000 years old (Photo 4-9). Several thin fractures lined with roots and fine sand were observed in trenches GMX-T1 and GMX-T2 (Figures 4-8 and 4-9; Photos 4-10,4-11 and 4-12). The fractures, which cut thinly laminated silt, clayey silt, and fine sand, show no discemable displacement, and prominent marker horizons in the upper Hookton Formation deposits can be traced across the upward (and downward) projections of the fractures with no displacement. The strata exposed in trenches WCC-11-T6a, GMX-T1, and GMX-T2 provide direct evidence for no significant faulting (more than about 2 centimeters) in strata at the foundation level of the ISFSI site since the late Pleistocene (during at least the past 80,000 years). No displacements were observed, and the stratigraphic contacts exposed in trench walls are sharp enough to preclude vertical fault displacements greater than about 2 centimeters. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-14 Section 4.0 Site Geology Rev. 0, September 16, 2002

4.6

SUMMARY

OF SITE GEOLOGY Knowledge of site geology is based on extensive studies of the stratigraphy beneath the site, regional mapping of the Little Salmon fault zone, trenching at the site, analysis of the geomorphology of the Buhne Point terrace, and review of recent studies of the Little Salmon fault. The primary elements of site geology are summarized below. The ISFSI site is underlain by a well-bedded sequence of Tertiary and Quaternary sedimentary rocks that contain excellent planar datums that record deformation on the Little Salmon fault zone and allow for estimation of deformation rates. Based on its relative topographic position and the presence of a strongly developed relict paleosol, the raised and tilted terrace surface (the Buhne Point terrace) at the ISFSI site formed during an interglacial high stand of sea level, and is correlated to either the 80,000- or the 1 05,000-year-old (Stage 5a or 5c marine terraces that are well preserved at other places along the northern California coast. The ISFSI site is on the hanging wall of the Little Salmon fault zone. Three branches of this fault zone-the Little Salmon, Bay Entrance, and Buhne Point faults-dip to the northeast beneath the site. The Little Salmon fault projects to the surface about 2.2 kilometers southwest of the ISFSI site. This fault either dies out south of, or is more than 1,600 meters below, the site. The Bay Entrance fault is the closest main splay of the Little Salmon fault zone to the Humboldt Bay ISFSI site. The fault projects to the surface about 500 meters west of the ISFSI site, and is about 410 to 470 meters from the site at its closest approach (fault-normal distance measured to the center of the site). The Buhne Point fault, a secondary splay in the hanging wall of the Bay Entrance fault, projects to the surface about 180 meters southwest of the ISFSI site and lies about 140 to 160 meters below the site. The southwest-dipping Discharge Canal fault splays off the Buhne Point fault daylighting near the Discharge Canal about 150 meters northeast of the site. Displacement on the Bay Entrance and Buhne Point faults uplifted the hanging-wall block between the main trace of the Buhne Point and Discharge Canal faults, tilting the Buhne Point terrace 2 to 4 degrees to the southeast. The tilted terrace surface reflects the tectonic deformation on the hanging wall of the Little Salmon fault zone, including ruptures Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-15 Section 4.0 Site Geology Rev. 0, September 16, 2002

associated with multiple earthquakes on the Cascadia subduction zone during the past 80,000 years. Despite the close proximity of the ISFSI site to active traces of the Little Salmon fault zone, the upper part of the lower Hookton Formation (about 310,000 years old) and the upper Hookton Formation deposits (>80,000 years old) are not faulted, as evidenced by continuous, unbroken upper Hookton strata in the near surface beneath the ISFSI site. These strata can be traced continuously across the ISFSI site with a high degree of resolution. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 4-16 Section 4.0 Site Geology Rev. 0, September 16, 2002

Horizon1 Depth (em) Moist A 0-35 10YR 2/2 BAt 35-52 7.5YR 4/4 Bt 52-96 7.5YR4/6 2Bt2 96-130 7.5YR 4/6 2Bt3 130-180 7.5YR 5-6/8 3Bt 180-230 10-7.5YR 5/8 3Cox 230-10YR 7/4 H:\\dmo\\5117.009\\Sec4\\4_Site Geol_ 9-16-02.doc 9/16/02 TABLE 4-1 DESCRIPTIONS OF SOIL PROFILES Pacific Gas and Electric Company Humboldt Bay ISFSI Color2 Texture3 Structure4 Consistence5 Mottles (moist) Moist Wet PROFILE JW-11* "" 100 M WEST OF ISFSI SITE 1 2 fg fr ss, ps 1-sci 2-3 m-e fi ss-s, p sbk sci 2-3 c pr fi s, p breaking to 2-3m-c sbk sci 2-3 c pr fi-vfi s, p breaking to 2-3m sbk c 1-2 d, 7.5YR 7/4 sci 1-2 c pr fi ss-s, p c 1-2 d-p, 10YR sicl 1-2 c pr fi-vfi s, p 7/4 f2 d, 10YR 6/8 & sicl M fi ss-s, p 4-17 Clay Films6 Boundary7 N.O. a-c, s 1-2 n pf & c, s po 2-3 n-mk po c, w &pf 2-3 mk-k pf c-g, s &po 1-2 n pf c-g, s 3-4 mk-k po 1-2 n pf a-c, w 2-3 n-mk po v1 n-mk po

Horizon1 Depth (em) Moist 270+ A 0-20 10YR 211 A2 20-43 10YR 3/1 B 43-75 7.5YR4/6 2Bt 75-140 7.5YR 5-6/8 2Bt 140-197 7.5YR 6/6 H:\\dmo\\5117.009\\Sec4\\4_Site Geol_ 9-16-02.doc 9/16/02 TABLE4-1 DESCRIPTIONS OF SOIL PROFILES Pacific Gas and Electric Company Humboldt Bay ISFSI Color 2 Texture3 Structure4 Consistence5 Mottles (moist) Moist Wet 7.5YR 6/8 PROFILE JW-12**....,130M EAST OF ISFSI SITE sicl 1m gr fr ss-s, p sicl 1m sbk fi s, p breaking to 2m gr sicl-sic 1-2 e-ve fi-vfi s-vs, p-pr vp breaking to 1m sbk m 2 d, 7.5YR 7/3 sic 2mpr fi s-vs, vp breaking to 3m sbk f2 d, 7.5YR 7/3 sic 1 c pr vfi s-vs, p-breaking vp to 2m 4-18 Clay Films6 Boundary7 c, s vl n pf c,w 1 n pf c, s 3 mk-kpf& c-g, s po 2-3 kpf & g,s po

Horizon1 Depth (em) Moist 2BCtc I97-232 7.5YR 6/6 3Cox 232-257 IOYR 5-6/4 4Cox 257-IOYR 6/4 327+ TABLE4-1 DESCRIPTIONS OF SOIL PROFILES Pacific Gas and Electric Company Humboldt Bay ISFSI Color 2 Texture3 Structure4 Consistence5 Mottles (moist) Moist Wet abk f-c 2 f, 7.5YR 6/4 c I cpr& vfi-efi vs, vp abk sl m fi ss, ps e-m 2-3 d-p, 7.5YR sicl m fi s, p 5/8 PROFILE GMX-T2*** SOUTHWEST CORNER OF ISFSI SITE A 0-5 lOYR 3/4 mostly stripped AlB 5-28 IOYR4/4 Bt 28-75 IOYR 3/6 Bt2 75-IIO IOYR 6/8 H:\\dmo\\5117.009\\Sec4\\4_Site Geol_ 9-16-02.doc 9/16/02 m 2 d, IOYR 7/3 m 2 d, IOYR 3/6 7.5YR 5/8 c m p, 7.5YR 8/2 sil-sl I m gr fr ss, ps sl I m sbk fi so,ps sci 2 e-ve cpr fi ss, p breaking to I m sbk sci 2 c cpr fi s, p breaking to 3m 4-I9 Clay Films6 Boundary7 3 kpf & po a-c, s a, s a, ir 2,n,po c-g, ir 3; mk; po g, ir 3 mk-kpf & g; ir po

Horizon1 Depth (em) Moist B/C 110-145 10YR 6/8 2Cox 145-213 7.5YR 4.5/8 3Cox 213-235 7.5YR 5.5/8 7.5YR 6.5/2 4Cox 235-362 7.5YR 5.5/8 7.5YR 6.5/2 4C 362-369 7.5YR N4/0 5C 369-7.5YR 420+ N4/0 H:\\dmo\\5117.009\\Sec4\\4_Site Geol_ 9-16-02.doc 9/16/02 TABLE 4-1 DESCRIPTIONS OF SOIL PROFILES Pacific Gas and Electric Company Humboldt Bay ISFSI Color2 Texture3 Structure4 Mottles (moist) abk m 1-2, d 7.5YR 6/8 sc 1-2 fabk m 1-2 d, 5YR 711 s-Is m sil m sil & s m s m sic m 4-20 Consistence5 Moist Wet fi s, p fi so,po fi ss, p fi ss, p so,po fr so, po s, p Clay Films6 Boundary7 3-4 k pf a, s va, s a, s va,w a, s

Soil profile exposed in steep south-southwest-facing escarpment below the Buhne Point terrace. Location shown on Figure 4-2. Soil profile exposed in steep north-northwest-facing escarpment below the Buhne Point terrace. Location shown on Figure 4-2. Soil profile exposed in northwest wall of trench GMX-T2 (station 180ft); relict paleosol formed on the Buhne Point terrace. Location shown on Figure 4-2. Explanation of Soil Descriptions 1 Master horizons: A = a surface horizon characterized by the accumulation of organic matter and typically as a zone of elluviation of clay, sesquioxides, silica, gypsum, carbonate, and/or salts; B =a subsurface horizon characterized as having a redder color, stronger structure development, and/or accumulation of secondary illuvial materials, such as clay, sesquioxide, silica, gypsum, and/or salts; C = a subsurface horizon that may appear similar or dissimilar to the parent material and includes unaltered material and material in various stages of weathering. Modifiers of master horizons: b =buried soil horizon; c =concretions or nodules; j =used in conjunction with other modifiers to denote incipient development of that particular feature or property; ox= oxidized (for C horizon only); p =plowing or other disturbance; t =accumulation of clay; w =color or structural B horizon. 2Color: From Munsell soil color chart (Munsell Color Company, 1988); dry colors were difficult to determine given very wet weather during fieldwork; --=not observed. Abundance: f= few, c =common, m =many. Size: 1 =fine, 2 =medium, 3 =large. Contrast: f = faint, d = distinct, p = prominent. 3 Texture: sl = sandy loam; Is = loamy sand; s = sand; 1 = loam; sci = sandy clay loam; sc = sandy clay; cl = clay loam; sil = silt loam; sicl = silty clay loam; sic = silty clay. 4 Structure: Grade: m =?massive; sg = single grain; v 1 = very weak; 1 = weak; 2 = moderate; 3 = strong. Size: f = fine; m = medium; c =coarse; vc =very coarse. Type: pl =platy; gr =granular; abk =angular blocky; sbk = subangular blocky; cpr = columnar; pr = prismatic. 5 Consistence Moist consistence: lo =loose; vfr =very friable; fr =friable; fi =firm; vfi =very firm; efi =extremely firm. Wet consistence: so= nonsticky; vss =very slightly sticky; ss =slightly sticky; s =sticky; vs =very sticky; po = nonplastic; vps =very slightly plastic; ps = slightly plastic; p = plastic; vp = very plastic. H:\\dmo\\5117.009\\Sec4\\4_Site Geol_ 9-16-02.doc 9/16/02 4-21

6 Clay Films: Frequency: v 1 = very few; 1 = few; 2 = common; 3 = many; 4 = continuous. Thickness: n = thin; mk = moderately thick. Location: br = clay bridges holding mineral grains together; pf = faces of peds; po = lining or filling tubular or interstitial pores; co= colloidal stains on mineral grains; N.O. =none observed;--= not observed. 7 Boundary with lower horizon. Distinctness: va =very abrupt; a= abrupt; c =clear; g =gradual; d =diffuse. Topography: s = smooth; w = wavy; i = irregular; b = broken. H:\\dmo\\5117.009\\Sec4\\4_Site Geol_ 9-16-02.doc 9/16/02 4-22

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EXPLANATION Post 1977 boring (ESAIWCC)

Pre 1978 borings (ESA) t------i Cross section

Seismic tines; SR Series: ESA; SL Series: WCC 500 1 000 1500 2000 ft 200 400 600 m Figure 4-1 Locations ofborings, cross sections, and seismic reflection lines used in the 1980 Woodward-Clyde Consultants report. (after Woodward-Clyde Consultants, 1980, Figure C-2). Cross section A-A' is shown on Figure 4-15 and cross section B-B' is shown on Figure 4-16.

m Humboldt Bay ISFSI Project Technical Report S TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

I / \\ Lithologic Units c=J Fill, man-made fill, and disturbed areas CJ Historicallandslide ~ Holocene alluv1um and marsh deposrts Pleistocene Hookton Fonnat1on Qph = undifferentiated Qpht = terrace surface Indicates areas where the surface IS disturbed EXPLANATION Map Symbols Lithologic contact, dashed where approximately located

? * ~~:~~~e~~~~~ ~~~~a~~~~~~~~~~i~a~~~le~cated; barb on upper plate A:'40*

~b~~t~r~~~~~~~~ nonnal fautt, bar and ball on '7b'_ 90 Stnke and d1p of reverse fault, barb on upper plate ~

Stnke and d1p of beddmg o,

3 Apparent d1p of bedding ~a* Stnke and d1p of fractures, double bar md1cates d1p d1rect1on

q. 7o*

Apparent d1p of fractures / Vert1cal fractures e ESA76-810 ~ Rotary wash borings with SPT blow counts (12 J) GMX-T2 _j__ ~ 11-TSA _.I.._ ~ BP-1 --L. Auger borings with SPT blow counts Borings with no blow counts Other borings from geologic investigations Spot elevation m feet from PG&E des1gn/ construction draw1ngs Geolog1c cross sect1ons shown on F1gures 4-5, 4-10, and 4-21 2-foot contour Interval (elevation above mean lower low water) Trench (th1s study), stat1ons 1n feet (see Appendix 4A) Trench of Woodward Clyde Consultants (1980) stations 1n meters (see AppendiX 4A) Trench of Earth Sc1ence Associates (1977), stat1ons 1n feet (see Appendix 4A) NOTE 1 Topographic survey made 1n 1999 and 2000 DERS7-1SC A OERBM OER87-15~0ERB7-15A 50 I 100 150 feet I 5 1 0 meters Figure 4-2 Geologic map of the ISFSI site. Humboldt Bay ISFSI Project Section 4.0 ~ 1 Technical Report Site Geology a TR-HBIP-2002-01 Rev.O, September 16, 2002

o> "0 9 ~ I ,!;?' ~ ~:S ~ ~ 0 0 ~ ~c-JE Ul 0 0 0/"' "0 I') "' j"O en a O.r:; C?_d ~~ <n>- /Z ooll:: on. 52~ "'o ..;:/ Ul/ I I I I I I I I 8 ~ EXPLANATION Map Symbols Lithologic contact, dashed where approximately located ~o* Normal fault; bar and ball on downthrown side ~3 Apparent dip of bedding / Vertical fractures ~ Rotary wash borings with SPT blow counts Borings with no blow counts Other borings from geologic investigations ("12.0) Spot elevation in feet from PG&E design/construction drawings 2-foot contour interval (elevation above mean lower low water)

t GMX-T 2 --L.. Trench excavated for this study; stations in feet

~ BP-1 _j_ Trench of Earth Science Associates (1976); stations in feet ~ 11-T6a ~ Trench of Woodward Clyde Consultants (1980); stations in meters Lithologic Units af I I laph,Qphtl Fill, man-made fill, and disturbed areas Historical landslide Pleistocene Hookton Formation Qph = undifferentiated Qpht =terrace surface Indicates areas where the surface is disturbed 30 I SCALE IN FEET UL-----------------------------------------------------------------------------------------------------------~ Figure 4-3 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Locations of geologic trenches and borings near the ISFSI site. Section 4.0 Site Geology Rev.O, September 16, 2002

i 9

g;'...

9 f:i

~- Base map: U.S. Coast and Geodetic Survey, 1858, Preliminary survey map of Humboldt, California. ¥ EXPLANATION 0..;. 0 0.5 Mile 0 1 Kilometer d Coastline from U.S.Geological Survey (1959) Fields Landing ~ ~ 7.5' Quadrangle, California

I C\\1 r--

~1 ~ Figure 4-4 Comparison ofthe shoreline shown on 1858 and 1959 surveys. The 1959 shoreline is superimposed 1 on the 1858 map to show the extensive coastal erosion and the retreat ofBuhne Point that occurred ro i£ prior to placement ofriprap along the shoreline of Humboldt Bay. 0 0 Humboldt Bay ISFSI Project ~&~ Technical Report TR-HBIP-2002-0 1 Section 4.0 Site Geology Rev. 0, September 16, 2002

West X X' I LANDSLIDE xz MAPPEOBV 1 ESA 19n X' I X' I SOUTH CORNER ISFSISito SAND \\NITH GRAVEL Dbt.ance(matera) ? Lithologic contact, dashed where approximate, queried where inferred. Note: Location of cross section is shown on Figure 4-2. Unit F location based on structure contour map (Figure 4-17). Stratigraphy above Unit F based on correlation of boreholes (ESA76-P2, GMX99-2, ESA76-6) and trenches (11-T6a, 11-T6b, 11-T6c). East X' Figure 4-5 Geologic cross section X-X 5

Humboldt Bay ISFSI Project

~ 1 Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev.O, September 16, 2002

HOOKTON FORMATION SCOTIA BLUFFS(?) FORMATION (Units OThrough V) ~ ~. *.o *. *:~ *.a:,.o, 0.~*~ *: M ~~.~ *~~ ci ~ ~........ <~ ~ Figure 4-6 Generalized stratigraphic section at the ISFSI site. See Sections 3.2.1 and 4.3 for basis of age estimates. (after Woodward-Clyde Consultants, 1980, Figure 7). .. Humboldt Bay ISFSI Project ~ ~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Depth (meters) Trench 11-T6b ~

~Disturbed Soil l'J r ~UnitS

-*~ ....a..-*- .:i?;E12 12 __::-..::_-=....

~

Trench 11*T6b > __.Unit7 >-.unitS z 0 ~ 6 g ~ I 2 0:: 0:: w 0 ~ LL ...J Trench 11-T6c _.UnitS 14 ___.Unit 5 __. Unit4 16 Trench 11-T6c _.Unit F 18 __.Unconformity

.~

-.unit3 ~ Unexposed Section ___.Disturbed Soil --.unit2 ~Unit1 __.Unconformity ~UnitF 28 -..:::::-.:::: c=l L.::J EXPLANATION Sand (s) Silt (sit) Silty clay/clayey silt (slt-cl/cl-slt) Gravel (Gr) Note: Section is a composite from trenches excavated in the Buhne Point terrace. Figure 4~ 7 Stratigraphic section of the uppermost lower Hookton and upper Hookton Formation exposed in Woodward-Clyde Consultants' trenches 11-T6a, 11-T6b, and 11-T6c {after Woodward-Clyde Consultants, 1980, Figure C-28). m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

70 50 40 i

g.

~ ~ 30 w -20 ~ 0 75 80 Southwest Wall --N75"W~ Distance (meters)" 85 Trench GMX-T1 Trench WWC-11-T6a -10 10 20 DESCRIPTION OF LITHOLOGIC UNITS Upper Hookton Formation (Late Pleistocene) UnitS: CJ 8 Unit 7: CJ 7v CJ ?lv ?lila CJ 7111 CJ 711 CJ 71 CJ Gleyed silty and sandy clay.Light gray to gray (10 YR 6/1 moist) and strong brown (7.5 YR 5/8 moist); some pel;>bles; moderately developed ped structure. Silty clay and clayey slit with some fine sand.Strong brown (7.5 YR 5/8 dry) with pinkish white (7.5 YR 8/2 dry) coatings along columnar and blocky ped faces; sand content increases with depth; very poorly stratified to massive; strongly oxidized; locally contains manganese-oxide nodules. Moderately sorted fine sand with silt and some clay.Mottled very pale brown (10 YR 7/3 dry) and reddish yellow (7.5 YR 6/8 dry) with light gray (5 Y 7/1) to gray (5 Y 6/1) coatings along ped faces; predominantly subrounded to subangular quartz sand; locally contains stringers of manganese-oxide nodules; NB indicates transition between A soil horizon, which has been stripped in most places (not mapped), and a Bt soil horizon developed on Unit 7v (see Table 4-1 for detailed soil profile description). Silty clay layer at the top of unit 7111* Fining-upward sequence of interbedded sand and silt. Dark grayish brown (2.5 YR 4/2) to gray (5 Y 5/2 moist) and strong brown (2.5 YR 5/2 moist) where oxidized; layers of well-sorted fine to medium sand interbeded with thin (<1 em ) lenses of silt grading upwards to clayey silt and silty clay; locally contains fine gravel along the basal contact; locally contains woody material. Silt interbedded with some fine sand and clayey silt. Dark gray; massive to weakly stratified layers of sandy silt and clayey silt with some lenses of fine sand and silty clay; bedding is discontinuous laterally. Silty clay.Dark gray; generally massive. 30 Distance (feet).. 40 90 95 Trench WWC-11-T6a 7u pproximate intersection with NW wall of Trench GMX-T2 50 60 EXPLANATION Lithologic contact; solid line where resolution is less than 2 em, dashed line where 2 to 5 em: dotted line where 5 to15 em. /Fracture NOTES:

values correspond to station numbers on original log of Trench 11-T6a (Woodward Clyde Consultants, 1980, Figure C-29). See Appendix 4A, Figure 4A-12.
- values correspond to station numbers on Trench GMX-T1.

(Geomatrix, 2002d). See Figure 4-2 for locations of trenches and ISFSI site. 70 100 80 15 14 13 ~ 12 ~ j 109 ~ .§.. 8 5 i w Figure 4-8 Composite log of trenches WCC-11 T6a and GMX-Tl. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

~

~~~

~~i 0 ~ ~ ~ + X ~ 0 C' o': g i2 ~ 1Ji j ))I ~ ~ ~ + ~+

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.s:: (/) 0 g. ) t ~:S 0 ~ ~ ~c-JE (/) 0 0 0/"' "0 I') "' ~ .s /"0 "'o O.s:: ~_d ~.2 ~~ Li)I- /Z (I)Cl:: ~~ Li)o ~/ (1)/ I I I I I I I I 8 ~

r:

~ Q) w 5 c 0 ~ Q) iii North y 20 10 0 ISFSI Site BAY CLAY SILT - - = = = = = = =.::-_- BAY CLAY - GRAVEL AND GRAVELLY SAND -10 -20 SAND WITH GRAVEL -30 BAY CLAY -40 UNIT F OF LOWER HOOKTON FORMATION --?-- -- --?-- -50 -? . --- *?- -60 -70 -80 -90 0 10 20 30 40 50 60 70 80 Distance (meters) -? Lithologic contact, dashed where approximate, queried where inferred. Notes: Unit F location based on structure contour map (Figure 4-17). Stratigraphy above Unit F based on correlation of boreholes (GMX99-2 through -5) and trenches, and outcrop exposure in bluff. South y1 70 50 0 -50 -100 ~ ~ c 0 :g Q)

iii

-150 -200 -250 90 UL_ ______________________________________________________________________________________________________ ~ Figure 4-10 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Geologic cross section Y-Y1. Location of cross section and boreholes are shown on Figure 4-2. Section 4.0 Site Geology Rev.O, September 16, 2002

rJ Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 DEPTH 50 100 150 HORIZON A /.-- AlB / / Bt \\.. *" \\ I / / ~ 8!2 l *'"'. / B/C 2Cox 3Cox 4Cox 5C Figure 4-11 Relict soil and upper Hookton Formation deposits exposed in trench GMX-T2 (NW wall at station 180ft.). See Table 4-1 for description of soil horizons. (Photographs FHS00/8-2#3 through FHS00/8-2#12 taken on August 1, 2000.) Section 4.0 Site Geology Rev. 0, September 16, 2002

..:.L1g'l A-11

_657 Elevation of fault in boring, in feet

Structure contour elevation, in feet Fault (projected surface trace)

At----fA' Cross section A-A' 500 1 000 1500 2000 ft 200 400 600 m .~ Figure 4-12 Structure contour map of the Little Salmon fault north of Humboldt Hill (after Woodward-Clyde Consultants, 1980, Figure C-14). Cross section A-A' shown on Figure 4-15. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-0 1 Section 4.0 Site Geology Rev. 0, September 16, 2002

_I t ...... _.:*.~ Ki11 0 EXPLANATION A-11

_657 Elevation of fault in boring, in feet

--2000- Structure contour elevation, in feet -'- ~ Reverse fault Bt----18' Cross section B-B 0 500 1000 ft 0 100 200 300m PLANT SITE Figure 4-13 Structure contour map of the Bay Entrance fault (modified from Woodward-Clyde Consultants, 1980, Figure C-18). Cross section B-B' is shown on Figure 4-16. m Humboldt Bay ISFSI Program Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev 0, September 16, 2002

S:\\51 00s\\5117\\5117.009\\task_13\\02_0725_s4\\_fig_04-14.ai B KING SALMON 0 Boring that clearly intercepts fault, depth indicated (feet) Boring that limits location of fault, depth indicated (feet) ()~ Borings that have the fault between them, depth indicated (feet) -- -400 Structure contour elevation (feet) _.._ Projected surface trace of Buhne Point fault based on topography, trench data, and boreholes .JUL1LJL Eroded fault scarp (fault-line scarp) B B' Cross section B-B' Note: Fault plane detected in WCC-7, 8, 9, and 11 only ? 0 100 200 300ft 0 25 50 75 100m Figure 4-14 Structure contour map of the Buhne Point fault {reinterpretation of data presented on Woodward-Clyde Consultants, 1980, Figure C-25}. Cross section B-B' is shown on Figure 4-16. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

A A' ~ c.5 E Humboldt Bay _..? - - ? -:-- - /. / ~ I Q..l 0 0 100 25 200 400 50 100 MSL -200 -400 -600 -800 -1000 600ft 150 200m Figure 4-15 Cross section A-A' across the Little Salmon fault zone at Humboldt Hill (modified from Woodward-Clyde Consultants, 1980, Figure C-15). Location of cross section A-A' is shown on Figures 4-1 and 4-12. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

B Q)

1 c Q)

~ c 0 Plant Site ~Humboldt Bay E ro CJ)

0) c ISFSI Site (projected) r Buhne Point terrace HOOKTON FORMATION King Salmon y-

\\ \\ "Unit F" Clay \\ \\ S2 I HOOKTON FORMATION Tank ~ HOOKTON FORMATION \\ SCOTIA BLUFFS(?) FORMATION ~\\ \\t ~ \\. ~~ ~,<;>),. 06> SCOTIA BLUFFS(?) \\ ~ FORMATION

v.

,~ \\.~ '~ \\%. -:,<;>)~ RIO DEL FORMATION ~ RIO DEL FORMATION Discharge canal HOOKTON FM. "Unit F" Clay HOOKTON FORMATION B' ....;) \\Note: Cross section modified from Woodward-e Bay Entrance and Buhne Point faults plotted from structural contour maps (Figures 4-14 and 4-15); contour intersection at fault shown as points. 0 500 m 0 1000 Vertical = Horizontal \\ Clyde Consultants (1980) (Figure C-8). \\ \\ ' 2000 ft Figure 4-16 Cross section B-B' across the Bay Entrance and Buhne Point faults. Location of cross section is shown on Figures 4-1 and 4-13. m Humboldt Bay ISFSI Project 'to. Technical Report a TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Buhne Point splay fault A.. ...... 1. ' ' -150 .~C60-9 - 1 52.~ \\ - - - - - - ' ~ ' - -170 ---180 --- -150- ? ---.4__ WCC80-8 e -148.40 WCC80-11-T6C e 26.00 300 feet 50 100 meters EXPLANATION Structure conto ~ 0 feet. Dashedu~~ontour interval ocated ere approximately Reverse fault d approximate!, I ashed where where inferre~ o~ated, queried plate arbs on upper Uncertainty in fault location Borehole sho. of Unit F in fwmg elevation oft eet op Tre:nch showin Umt F, in feet 9 elevation of top of Figure 4-17 Structure co H ntour map f .. umb_oldt Ba IS o top of Unit F. ~: 1 Techntcal R y FSI PrOJCCt TR-HBIP-2oe62~~~ . Section 4.0 Rev 0 s Stte Geolo . ' eptember 16, 20g

I(I"IUIIf* ~ O I I TA~a,_,, I I LITHOLOGIC DESCRIPTIONS UNIT7: SAND Brown to dark brown (1 0 YR 4/3 moist), dark yellowish brown (1 0 YR 4/6 moist), and yellowish red (5 YR 4/6 moist); fine-to medium-grained; subrounded; contains some discontinuous silty clay laminae and very thin beds (1 to 5 em). INTERBEDDED AND INTERMIXED SILT, SAND, AND SILTY CLAY Pale brown (10 YR 6/3 moist), strong brown (7.5 YR 5/8 moist), and dark gray (2.5 Y N/4 moist). SILT Strong brown (7.5 YR 5/8 moist), light olive-brown (2.5 Y 5/4 moist), and dark gray (2.5 Y N/4 moist); discontinuous interbeds of lenses of silty clay and fine-grained quartz sand. SILTY CLAY I CLAYEY SILT Dark gray (2.8 Y N/4 moist); slightly sticky and slightly plastic; many organic fragments, some pyritized. INTERBEDDED AND INTERMIXED SILT AND SAND Unit fines upward. Yellowish red (5 Y 5/8 moist) and strong brown (1 0 YR 5/8 moist); sediment deformation common. UNIT 6: SILT, SILT WITH SAND LAMINAE, MEDIUM AND COARSE SAND Unit fines upward. Strong brown (7.5 YR 5/8 moist), yellowish brown (1 0 YR 5/8 moist), light olive-brown (2.5 Y 5/4 moist). Sediment deformation in uppermost silts. Basal pea-sized gravel. UNIT 5: SILT, SILT AND SAND, FINE AND MEDIUM SAND Unit fines upward. Light olive-brown (2.5 Y 5/4 moist), and grayish brown (2.5 Y 5/2 moist). Basal pea-sized gravel or sand interfingers with underlying silt. UNIT 4: SILTY, PEATY SILTY SAND, SILTY SAND WITH SOME PEBBLES, GRAVEL Unit fines upward. Dark yellowish brown (1 0 YR 4/6 moist), yellowish red (5 YR 4/6 moist), light olive-brown (2.5 Y 5/4 moist), and grayish brown (2.5 Y 5/2 most); abundant organic material at base of silt and within peat layer. Gravel is subangular, poorly sorted and poorly graded; coarse sand size to 30 em; 46 percent chert, 37 percent quartz-rich metavolcanic and metasedimentary rocks, 13 percent quartz, 4 percent graywacke sandstone, 2 percent clay balls, rare sand lenses. UNIT3: SAND Olive-brown (2.5 Y 4/4 moist); medium-grained; subrounded to subangular; contains discontinuous thin (2 mm to 4 em) silt lenses. 'L__ ___ _L _ _ _t__--1 f---t 0 3 ft HorizOntal = Vertical Q}111 n,Mt M3tW, !J)S (i) ll l 3¥1,!11. 5 (D tU o fO, ~ $ {i) lf iSW,,S IUI'III,,_ S @ Mz,w. sn oo..,....., lt ~ l ". ~' Nl 1W,5l l @ III SW,n5 @) ~~~ * **5 1!. e N1 7 W, >0 5 @ NZI)W,l'U

8*

fri 12W, :".U @ II Uiii, U S W H *. 6c ~ @ f'I U W,715 1UlW,50~ 0 N U W, r.G~ 0 IH IW,,l!i 8 OII:O W, CU t} NI4 C, H " 8 II I U , S8 ::0 N ~)w,n~ 8 Nl...,)IS {'t N"'.,, tGS 114411',"" @l ~ : *. ~ * :r. @) "ZII W,IU ,g....... 6 N G~, 4 l:l NllW,,CS 8 0110.... 51~ ~ frM.,,lU Log of trench 11-T6b showing small faults of the Buhne Point fault in the lower Hookton Formation {from Woodward-Clyde Consultants, 1980. Figure C-35). Location of trench is shown on Figure 4-2. @) ~ O*&U ~ """' @ 1124...., 4 11 e N ) HI', 2U {., II41W, S7!i S "n w,us 8 N M\\If, S U Q ll ooCW,2tll @ Nl SII¥,4 l!i t!9 N l ow, ~ 41 EXPLANATION Lithologic contact; solid line where resolution is less than 2 em, dashed line where 2-5 em, dotted line where 5-15 em. Soil contact Disturbed soil contact

.~N 7

~

5

'H*

W ~>J "'"'~~~;! Fault; solid line where resolution is less than 2 em, dashed line where 2-5 em, dotted line where 5-15 em; strike and dip SON of fault plane indicated; arrows indicate sense of relative displacement. N70W 55N.....,..- Strike and dip of jointing Shears Figure 4-18 Log ofWCC trench 11-T6b. Humboldt Bay TSFSI Project ~ ~.~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

--1 0 1m f----------r 0 3ft. Horizontai=Vertical LITHOLOGIC DESCRIPTIONS UNIT 2: SAND WITH SILT INTERBEDS Yellowish brown (10 YR 516 moist) and light brownish gray (2.5 Y 6/2 moist); fine-to medium-grained; laminated, some sediment deformation and cross-bedding. UNIT 1: INTERBEDDED SAND AND GRAVEL Gravel: 1 mm to 15 em; poorly sorted and poorly graded; thinly bedded; 53 percent chert, 23 percent metavolcanic and metasedimentary rocks, 11 percent quartz, 11 percent graywacke sandstone, 2 percent clay balls. Sand: Strong brown (7.5 YR 4/6 moist); massive; medium-grained; subangular. UNIT F: SILTY CLAY Very dark gray (10 YR 311 moist); slightly sticky and slightly plastic silty clay; rare shattered sea shells. Grades to interbedded and intermixed silt and sand. Unit fines upward. Interbedded and intermixed silt and sand is dark brown (7.5 YR 314 moist) and dark grayish brown (10 YR 412 moist). Sand is olive-brown (2.5 Y 414 moist); medium-grained; subrounded to subangular; contains some discontinuous, thin (2 mm to 4 em) silt lenses. EXPLANATION Lithologic contact; solid line where resolution is less than 2 em, dashed line where 2-5 em, dotted line where 5-15 em. Soil contact

- - * *- **- Disturbed soil contact Log of trench ll-T6c showing small faults of the Buhne Point fault in the lower Hookton Formation (from Woodward-Clyde Consultants, 1980, Figure C-35). Location of trench is shown on Figure 4-2.

~:- 7

'f~1{i+/-&i Fault; solid line where resolution is less than 2 em, dashed line where 2-5 em, N75W dotted line where 5-15 em; strike and dip 60N of fault plane indicated; arrows indicate sense of relative displacement.

N70W 55~ Strike and dip of jointing Shears Figure 4-19 Log ofWCC trench ll-T6c. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

l I

. ?
r=*

l ji LITHOLOGIC DESCRIPTIONS McKINLEYVILLE TRENCH LOGS 11-T3a,11-T3b& 11-T3c Unit4: Soil 3b: 4a: Turbated B Horizon Yellowish brown (10 VA 2/1 moist) and dark yellowish Same as 3a only less clay. Horizontai:::Vertical brown* ( 10 Y R 3/4 moist); slightly sticky and slightly U::<.n'-"i-'-'t 2"-':___,M.:.ca,_r'-'-'in:o:..e _,_T"'er_,_,ra"'ce._DO<:e,.p'-'<o,.,_sit,..s plastic friable sand loam; weakly developed medium crumb ped structure. Contains some pebbles. 4B: A Horizon Black (10 YR 2/1 moist), slightly sticky and slightly plastic, friable to loose sand loam. Ped structures weakly developed." Contains burrows and rqots. 2a: Gravel Pebbles and cobbles in a light olive-brown (2.5 Y 5/4 moist). fine-to medium11rained sand matrix (approxi-mately 15 percent of unit): moderately sorted. 2b: Terrace Sand EXPLANATION Lithologic contract; solid where resolution is less than 2 em, dashed line where 2-5 em, dotted line where 5-15em. Soil contact Unit 3: Colluvium Pale olive (5 VA 6/4 moist); fine11rained; subangular; moderately to well sorted; friable; cross-bedded. ---Disturbed soil contact 3a: Olive-yellow (2.5 YR 6/6 moist), fine-to medium-grained subangular, moderately sorted, friable to slightly indurated sand; randomly oriented pebbles and cobbles. Unit 1: Crannell Brown Sand Yellowish brown (10 YR 5/6 moist); fine11rained; sub-angular, 70 to 80 percent quartz and 20 to 30 percent lithic fragments; moderately to well sorted; friable to slightly indurated. McKinleyville trench (from Woodward-Clyde Consultants, 1980, Figure B-19a). Location of trench shown on Figure 3-3. ~'~l ~ ~..... _ __*....

~---*... :.. ~1!

- *I I I Fault; solid line where resolution is less than 2 em, dashed line where 2-5 em. dotted line where 5-15 em; strike and dip of fault plane indicated; arrows indicate sense of relative displacement. 55~ Strike and dip of jointing --:,-!f:!r Shears Figure 4-20 Log ofWCC {1980) trench at McKinleyville. Section 4.0 Site Geology Rev. 0, September 16, 2002

West-Southwest w BUHNE POINT FAULT I BUHNEPOINT SPlAY FAULT I LIMIT OF MAPPING OFUPPERHOOKTON -~v~L~TH~~"Y~__:-_:--- - ~ Fault, dashed where inferred, arrows show sense of displacement.

?

Lithologic contact, dashed where approximate, queried where inferred. Note: Location of cross section is shown on Figure 4-2. Unit F location based on structure contour map (Figure 4-17). Stratigraphy above Unit F based on correlation of boreholes (ESA76-P2, GMX99-2, ESA76-6 through -8) and trenches. See Figure 4-2 for locations of boreholes. BAY ClAY UNIT F OF LO'NER HOOKTON FORMATION Dlc.Wr.oo(molors) I I I DISCHARGE CANAL East-Northeast W' I I -1 I ,g --- --- ~---- ----------------- -150~ I ____ __; r ----------- I Figure 4:21 Geologic cross section W-W: ~ Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev.O, September 16, 2002

50 K ~ 0 100 150 Exposure of Discharge Canal fault in sea cliff west of Discharge Canal. The vertical string line in the middle of the photograph is 100 em long. (Photographs JW-3-23 and 24; taken on March 21, 2000). Location of exposure is shown as outcrop JW-7 on Figure 4-2. .--N43E 50 em 2ft. Horizontal =Vertical 1AJ '< N17W, 87NE liD'< N17W, 87SW (g '< N60W, 90+/-

- - - ---- Fault, dashed where approximately located; dotted and queried where inferred Lithologic contact, S = soil contact Bt horizon

@)Sandy clay, with fragments of@ @Sandy clay - clayey sand Sand (clayey), prominent dark horizon in photograph G) Silty clay Cross trench strike of zone (shearing) -N50W Figure 4-22 Exposure of Discharge Canal fault. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

25 20 10 NE I 11+<16 I I t:t+<l.l I I t:t+.n I I 11 +~* I I D +~~ I rtf W tDUTJEA!T I 3ft Horizonlai=Vertical , +'* I I 11 +,., I Log of northeastern part of trench BP-2 {from Earth Sciences Associates. 1977, Figure C37 [colors added for emphasis]). Station numbers are in feet. Location of trench is shown on Figure 4-2. I D+o* I sw Log southwest of here not shown Science! Figure 4-23 Log ofESA (1977) trench BP-2. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

20 10 10 ~ Spoil pile contacts not shown ~ 15 View West Logged by T.D. Hunt 20 25 10 11 Log of trench BP-3 {from Earth Sciences Associates, 1977, Figure C37 [colors added for emphasis]). Station numbers are in feet. Location of trench is shown on Figure 4-2. 11~ If rt(ICII lf'JU: *I' HTIICt 11 I~HI fOTFJ.U 45fe(lt 13meters Figure 4-24 Log of ESA (1977) trench BP-3. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

(a) Fault CH-4 CH-3 (b) Cut-and-Fill Channel CH-4 CH-3 0 3m 0 10ft Vertical = Horizontal CH-2 CH-1A CH-2 CH-1A CH-5 elevation --160 (MLLW) CH-5 elevation --160 (MLLW) Figure 4-25 Alternative interpretations of the irregularities in the top of the Unit F clay between boreholes WCC80-CH4 and WCC80-CH5. Locations of boreholes shown on Figure 4-2. .. Humboldt Bay ISFSI Project ~ ~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

A) View toward the southwest. B) View toward the west-southwest. [}{]~ ~~ Photo 4-1 Oblique aerial view of the Humboldt Bay ISFSI site. (Photographs taken July 25, 2000, by W. D. Page.) .. Humboldt Bay ISFSI Project ~J.. ~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-2 Oblique aerial view looking northwest from above Humboldt Hill toward the entrance of Humboldt Bay. (Photograph taken july 25, 2000, by W. D. Page.) .. Humboldt Bay ISFSI Project r!tfl~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-3 View looking west from Buhne Point showing the escarpment along the north side of the Buhne Point terrace and riprap along the shoreline of Humboldt Bay. (Photograph JW-2-1 taken March 9, 2000.) .. Humboldt Bay ISFSI Project ~ ~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

S:\\51 OOs\\5117\\5117.009\\task_13\\02 _ 0725 _s4\\_photo _ 04-04(05).ai ISFSI Site Unit 3 Photo 4-4 View to east of Buhne Point terrace surface and ISFSI site. (Photographs JW-2-5 and JW-2-8 taken March 10, 2000.) m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

S:\\51 OOs\\5117\\5117. 009\\task_13\\02_ 0725 _ s4\\_photo _ 04-05(03,04 ).ai (A) ~ Meteorlogical Tower (B) Unit~ 3 ~ Meteorlogical Tower Photo 4-5 Oblique aerial photographs showing disturbance of Buhne Point terrace during trenching activities by Earth Sciences Associates (circa 1975). (A) View to the west-southwest. (B) View to the east-southeast. m Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-6 Outcrop of sand with interbedded silt (light layers) in sea cliff north of ISFSI site. Scale is in tenths of feet. View to the south-southeast. (Photograph JW-1-9 taken March 2, 2000.) .. Humboldt Bay ISFSI Project J'FD ~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-7 Trench GMX-T1, view east-southeast. View along trench with Humboldt Bay Power Plant in the background. Part of trench GMX-T2 is in the foreground. (Photograph FHS-00/8-1

29 taken August 1, 2000.)

.. Humboldt Bay ISFSI Project ~ ~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-8 Surveying geologic contacts in trench GMX-T2. View is toward the south. (Photograph FHS-00/7 -4 #9 taken August 1, 2000.) .. Humboldt Bay ISFSI Project r!t'f~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-9 Artificial fill overlying sand and silt layers of the upper Hookton Formation in northwest wall of trench GMX-T2 between station 36 ft. and station 44 ft. (Photograph FHS-00/7 -4 # 19 taken August 1, 2000.) Fill .. Humboldt Bay ISFSI Project ~~~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-10 Clay fractures in upper Hookton Formation in trench GMX-T2. Fractures are at station-25ft., depth -5 ft. Note continuous bedding across fractures below where they have been bleached in the weathered silty clay. (Photograph FHS-00/8-3

32 taken August 3, 2000.)

.. Humboldt Bay ISFSI Project !!~'&~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-11 Fracture lined with black compressed rootlets in clayey-silt bed in trench GMX-T2. Fracture is at station 40ft., depth -11 ft. (Photograph FHS-00/7 -3 #21 taken August 3, 2000.) .. Humboldt Bay ISFSI Project rFs~ Technical Report TR-HBIP-2002-01 Section 4.0 Site Geology Rev. 0, September 16, 2002

Photo 4-12 Continuous bedding across bleached fracture in silty clay in trench GMX-T2. Fractures are at station 30 ft., depth ~4 ft. (Photograph FHS-00/8-3 #26 taken August 3, 2000.) .. Humboldt Bay ISFSI Project ~~ Technical Report TR-HBIP-2002-01 Silty Clay Section 4.0 Site Geology Rev. 0, September 16, 2002

Section 5.0 Seismic Source Characterization

5.1 INTRODUCTION

Interpretations of the tectonic framework of the Mendocino triple junction region have evolved rapidly during the past few decades as new geologic, seismologic, and crustal structure information has become available. In particular, the characterization of the Cascadia subduction zone has changed dramatically (see Section 2.0). Prior to the mid 1980s, the Cascadia subduction zone was judged not to be seismically active by the majority of seismologists and geologists, and was interpreted not to have the capability of producing significant earthquakes. As new geologic evidence was identified during the mid and late 1980s, the perception of the capability of the subduction zone changed, and by the mid 1990s, a new scientific consensus that the subduction zone is capable of generating great earthquakes had evolved (Atwater and others, 1995). Because the scientific community increasingly accepted the Cascadia subduction zone as a potential source for earthquakes, the California Seismic Safety Commission, along with the California Department of Transportation (Caltrans) and the Oregon Department of Transportation, sponsored studies to define the characteristics and assess the consequences of a Cascadia subduction earthquake. In California, the California Division of Mines and Geology (CDMG) prepared a Cascadia earthquake scenario analysis (Toppozada and others, 1995). The CDMG scenario earthquake was defined as a "Gorda segment" rupture, involving slip on the southern 240 kilometers of the Cascadia interface and generating a magnitude 8.4 earthquake 1* Additionally, the CDMG scenario event included slip on the Little Salmon fault zone that was triggered by slip on the subduction interface. The Little Salmon fault zone was interpreted to be 1 Earthquake magnitudes are moment magnitudes, M, unless otherwise stated. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 5-1 Section 5.0 Seismic Source Characterization Rev. 0, December 27,2002 I

a crustal thrust fault above the Cascadia interface. The scenario earthquake was also considered to be a source for generating a local tsunami. 5.2. DESIGN INPUTS 5.2.1 Width Approaches for Cascadia Interface The width of the Cascadia interface depends on the location of the updip (shallowest point) and downdip (deepest point) limits of potential seismogenic rupture. Geomatrix (1995, page 2-21) gives two alternative models for the location of the updip limit and two alternative models for the location of the down dip limit. The updip extent is defined by either the location of the deformation front or the location of the change in structural trends near the slope break (change in fold trends). Geomatrix (1995, p 2-

21) estimates that fault width using the change in fold trends boundary is 25 km less than using the deformation front boundary. Geomatrix (1995, page 2-21) gives relative weights of 0.7 to the change in fold trends model and 0.3 to the deformation front model.

The down dip extent is defined by either the location of the zero isobase line or the midpoint of the transition zone defined by the thermal and geodetic modeling. Geomatrix (1995, page 2-21) gives relative weights of 0.6 to the zero isobase model and 0.4 to the thermal-geodetic model. On page 2-21 of Geomatrix (1995), the width of the Cascadia interface is given for the four combinations of the locations of the updip and down-dip limits, but the values are not correct. It appears that they incorrectly used the location of the change in fold trends as the location of the deformation front and the change in the fold trends was placed 25 km east of the misplaced deformation front. The result of this error is that interface widths listed in Geomatrix (1995) are too small. New calculations of the width of the interface are made in section 5.4.1 below. Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-0 1 5-2 Section 5.0 Seismic Source Characterization Rev. 0, December 27, 2002

5.2.2 Dimensions of the Cascadia Interface Rupture Lengths Carver (2002c) models the Cascadia interface as a combination of the Cascadia interface, Little Salmon fault zone, and Table Bluff fault. The alternative models for the lengths of the Cascadia interface ruptures and the weights for the alternatives given by Carver (2002c) are listed in Table 5-1. Dip Cohee et al. (1991, p. 37, caption to Figure 3) give the dip of the interface of 11° in Washington and 21° in Oregon. The average value of 16° degrees is used for the fault rupture. 5.2.3 Little Salmon Fault Zone Rupture Length Carver (2002c) defines the Little Salmon fault zone as extending from the Yager fault to the Thompson Ridge fault (PG&E, 2002a, Figure 2-5). The length of the zone is 310 km (Carver 2002c, pg 5A-6). Dip Carver (2002c) gives three possible dips of the fault of 40, 45, and 50 degrees; weights on each are 0.2, 0.6 and 0.2, respectively. Crustal Thickness The thickness of the crust in the HBIP region is given as 15 km (Carver, 2002c). Displacement per Event The fault displacement is given as 7m or 9.3m (equally likely) (Carver, 2002c). Style of Faulting The Little Salmon fault is a reverse slip fault (Carver, 2002c). Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 5-3 Section 5.0 Seismic Source Characterization Rev. 0, December 27,2002

5.3 METHOD AND EQUATION

SUMMARY

5.3.1 Method The magnitude of the Maximum Credible Earthquake is computed based on the mean magnitude determined for the maximum rupture area or fault displacement 5.3.2 Equations Magnitude-Area Relations The Wells and Coppersmith (1994; Table 2A, p. 990) scaling relation for magnitude as a function of rupture area for crustal faults (using all fault types) is given by M = 0.98 Log(A) + 4.07 (5-1) where A is the rupture area in km2 and M is moment magnitude. The Abe (1981;1984) relation for magnitude as a function of rupture area for subduction zones is given by (Geomatrix, 1995, p. 2-29) M = Log(A) + 3.99. (5-2) The Geomatrix (1993) relation for magnitude as a function of rupture area for subduction zones is given by (Geomatrix, 1995, p. 2-29) M = 0.81 Log(A) + 4.7 (5-3) Magnitude-Displacement Relations The Wells and Coppersmith (1994; Table 2B, p. 991) scaling relation for magnitude as a function of average fault displacement for crustal faults (using all fault types) is given by M = 0.82 Log(D) + 6.93 Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 5-4 (5-4) Section 5.0 Seismic Source Characterization Rev. 0, December 27,2002

where D is the average displacement over the rupture surface in m. Downdip Width The following illustration is used for Eqns. 5-5 and 5-6. X <:-------------~ I I :y I 'f For a fault with dip b'and horizontal extent X, the downdip width, W, is given by W= X cos(b') (5-5) For a fault with dip b' and vertical extent Y, the downdip width, W, is given by W=-y-sin(b') Eq. (5-5) and (5-6) are well known trigonometric relations. Weighted Average (5-6) Given N values~ with weights wt;, the weighted mean is (Bevington, 1969, p. 73) N _Lxiw( Mean = --=-i=--=-1 --- N L wti i=l Humboldt Bay ISFSI Project Technical Report TR-HBIP-2002-01 5-5 (5-7) Section 5.0 Seismic Source Characterization Rev. 0, December 27,2002}}

ML14045A367

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ML14045A367

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4.1 INTRODUCTION

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5.1 INTRODUCTION

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