ML24351A190

Comment (44) E-mail Regarding Diablo Canyon Lr Draft EIS

ML24351A190
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Site:	Diablo Canyon
Issue date:	12/16/2024
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NRC/NMSS/DREFS
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89FR87433
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Luster, Tom@Coastal <Tom.Luster@coastal.ca.gov>

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[External_Sender] Coastal Commission comments on Diablo Canyon Draft DEIS Supplement 62 Attachments:

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12/16/2024 2:53:48 PM Coastal Commission comments on Diablo Canyon DEIS Supplement 62 Dec 16 2024.pdf 258299 Options Priority:

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STATE OF CALIFORNIA - NATURAL RESOURCES AGENCY GAVIN NEWSOM, GOVERNOR CALIFORNIA COASTAL COMMISSION ENERGY, OCEAN RESOURCES AND FEDERAL CONSISTENCY 455 MARKET STREET, SUITE 300 SAN FRANCISCO, CA 94105-2421 VOICE (415) 904-5200 December 16, 2024 TO:

Nuclear Regulatory Commission Mail Stop TWFN-7-A60M Washington, D.C. 20555-0001 VIA:

DiabloCanyonEnvironmental@nrc.gov RE:

Docket No. NRC-2023-0192 - Comments on Generic Environmental Impact Statement for License Renewal of Nuclear Plants - Draft Supplement 62 Regarding License Renewal of Diablo Canyon Nuclear Power Plant, Units 1 and 2 (Draft Supplement)

Thank you for the opportunity to comment on the above-referenced Draft Supplement regarding the application submitted by Pacific Gas and Electric Company (PG&E) to renew the operating licenses for Units 1 and 2 at the Diablo Canyon Nuclear Power Plant (Diablo Canyon) near Avila Beach, for an additional 20 years. The California Coastal Commission (Commission) implements the federal Coastal Zone Management Act (CZMA) of 1972 as it applies to federal activities, development projects, permits and licenses, and it provides support to state and local governments. The federal government certified the California Coastal Management Program (CCMP) in 1977. The enforceable policies of that document include Chapter 3 of the California Coastal Act of 1976. Renewal of PG&E's operating license is subject to federal consistency review by the Coastal Commission pursuant to the CCMP and the associated federal regulations at 15 Code of Federal Regulations (CFR) 930 et seq.

As noted in previous communications from our agency, because the federal action being evaluated by the NRC is a 20-year license extension for operating Diablo Canyon, the Commission will be reviewing PG&Es proposed license renewal pursuant to PG&Es request for a consistency certification and its expected submittal of a coastal development permit (CDP) application for development activities associated with continued power plant operations. The Commissions primary evaluation of the proposed relicensing will occur through review of those applications; however, we are providing the comments below to identify several key elements of our review that may be useful in the NRCs consideration of license renewal.

Comments Section 2.2.2 - Refurbishment Activities: The Draft Supplement at pages 2-10 and 2-11 states that as a result of PG&Es evaluation of the facilitys structures, systems, and components (SSCs), it did not identify the need to undertake any major refurbishment or replacement activities to support the continued operation of Diablo Canyon as part of license renewal. However, PG&E has more recently identified several proposed additional

Coastal Commission comments on Draft Supplement 62 December 16, 2024 2

development activities that would be incorporated into the facilitys period of extended operations and that would be subject to review and approval of CDPs by the Commission and/or San Luis Obispo County. These include partial relocation of a road near an area used for onsite transport of spent fuel, slope stabilization work, refurbishment and expansion of a retaining wall, installation of new charging equipment, and others. PG&E has also stated that it may soon propose several additional activities. We recommend the NRC incorporate and analyze these projects as part of a subsequent Draft Supplement.

Section 3.1 - Affected Environment, Environmental Consequences, and Mitigating Actions: Page 3-1 of the Draft Supplement states that the NRCs review is based on the current site conditions that have resulted in part from the past several decades of Diablo Canyon operations. It also states that environmental conditions have adjusted to the presence of the facility. This is not the case for some coastal resources affected by the facilitys operations, for which the Commission will be applying standards under Chapter 3 of the Coastal Act to evaluate the effect of extended operations. For example, the facilitys ongoing impacts on marine life (primarily those resulting from entrainment due to the intake of seawater for cooling) are typically evaluated by calculating an annual loss of marine life productivity that occurs during each year of facility operations. Our current assessment shows that these operations, which would end if not for license renewal, result each year in the equivalent of several hundred acres of lost marine productivity (see additional comments below on Sections 3.5 and 3.7). Please note, too, that the U.S. EPA has recommended that PG&E conduct an updated entrainment study to identify impacts that may be substantially different than those identified in PG&Es prior studies that are now more than 15 years old1 We recommend this be reflected in Tables 3-1 and 3-2 and in the subsequent relevant descriptions of surface water and aquatic resource impacts.

Additionally, page 3-7 acknowledges that PG&Es application for federal consistency certification is not yet complete. Coastal Commission staff is working with PG&E to resolve this issue and is nonetheless continuing to evaluate the partial application for consistency with the CCMP and is expecting PG&E to also submit a complete application for a CDP.

Section 3.4 - Geologic Environment: The Draft Supplement states on page 3-27 that the NRC staff did not identify any new and significant information related to geology and soils that would change the environmental impact determination stated in the LR GEIS (NRC 2024-TN10161) for this Category 1 generic issue and that no significant impacts on geology and soils are anticipated during the LR term that would be different from those occurring during the current license term. As noted above, however, PG&E has identified at least two planned projects that involve geologic considerations - relocation due to coastal erosion of part of a road in an area used to transport spent fuel and repair of a slope failure within the Owner Controlled Area - that we recommend be evaluated as part of a subsequent Draft Supplement.

1 Importantly, entrainment impacts are evaluated on an annual basis - i.e., how much marine life productivity is lost during each years operation - and any mitigation that may be required is based on the expectation that it provide compensatory productivity during each year of operation.

Coastal Commission comments on Draft Supplement 62 December 16, 2024 3

There are also at least two other recent sources of information that we recommend the NRC incorporate into its Draft Supplement analyses. First, Californias Independent Peer Review Panel (IPRP) evaluated PG&Es recent 2024 Updated Seismic Assessment and identified several aspects of PG&Es seismic evaluations that would benefit from additional data collection and analysis to better characterize seismic risks at and near Diablo Canyon. We have attached to this letter a technical memorandum prepared by the Commission staffs engineering geologist describing the IPRPs evaluation and the additional information it requested PG&E provide by October 26, 2024. We recommend that the NRCs analyses incorporate the IPRPs review and any forthcoming response provided by PG&E. Commission staff has also requested PG&E provide this information as part of its complete application for federal consistency certification and for a CDP.

Additionally, the NRC has recently determined that two issues raised in a recent petition regarding the proposed relicensing will be subject to further review by NRC staff. As stated in the NRCs December 5, 2024, letter to PG&E (#EPID L-2024-CRS-0000), the NRC will be investigating potential underestimates in PG&Es seismic source characterizations and its choice of a model characteristic thrust earthquake for comparing local characteristics. We recommend that results of these additional evaluations be incorporated into subsequent versions of the Draft Supplement.

Section 3.5 - Water Resources: Page 3-31 of the Draft Supplement describes potential flood hazards along the Diablo Canyon shoreline, including those resulting from tsunami, wind generated storm waves, storm surge, and tides. PG&Es 2016 analysis found that the cumulative effects of a probable maximum storm surge and seiche with wind-wave activity combined with an antecedent 10 percent exceedance high tide yielded wave heights of 41.7 and 9.9 feet above mean sea level (MSL) outside and inside the breakwaters, respectively. The estimated wave heights along the coastline were 43 to 75 feet below the power block elevation of 85 feet MSL. We recommend the Draft Supplement either clarify that these estimates included various projections of sea level rise (SLR) in conjunction with storm (annual, 10-year, 20-year, and/or 50 year) activity and non-storm activity over the next 20 years or that the analyses be revised to include the most recent SLR and storm activity projections, including the Extreme Risk Aversion (H++)

scenario applicable to critical infrastructure projects such as Diablo Canyon.

Additionally, page 3-36 discusses the state Regional Water Quality Control Boards expected review of an updated NPDES permit for Diablo Canyon and states that PG&E does not expect an updated permit to be different than the current one. However, the states water quality standards have undergone several substantial changes since PG&E received its current NPDES permit more than 30 years ago, and we understand that an updated NPDES permit will need to incorporate those changes, several of which could result in necessary changes to Diablo Canyons effluent limitations and operational requirements. We recommend the Draft Supplement describe the water quality standards changes and evaluate any likely modifications to Diablo Canyon that may result from these changes. Please note, too, that the U.S. EPA has recommended that PG&E conduct an updated entrainment study for use in the Regional Boards upcoming review. This updated study is expected to better characterize the loss of marine life productivity associated with extended cooling water intake operations.

Coastal Commission comments on Draft Supplement 62 December 16, 2024 4

Section 3.6 - Terrestrial Resources: The Draft Supplement notes on page 3-60 that some of the Diablo Canyon lands are considered Environmentally Sensitive Habitat Areas (ESHAs) under the Coastal Act and CCMP; however, it does not incorporate that designation in its descriptions or analyses of the various habitat areas in these lands. We recommend the document be revised to note that a significant proportion of the Diablo Canyon lands are considered ESHA, that the Coastal Act and CCMP allow for limited specified uses in those areas, that disturbance in those areas is generally considered significant, and that development activities in or adjacent to those areas would likely be subject to coastal development permit requirements. We recommend the Draft Supplements description of terrestrial resources include a more comprehensive description of the ESHA within and adjacent to the project area and the expected and potential impacts to any nearby ESHA.

Section 3.7-Aquatic Resources: The document states on page 3-71 that aquatic resource impacts from license extension are expected to be small and on page 3-80 that operations would likely not destabilize or alter important attributes of the aquatic environment. It further states that several marine species have acclimated to the effects of facility operations (see, for example, page 3-122s discussion of sea otters). However, as noted above, each year of Diablo Canyons cooling water intake operations results in the continual annual loss of marine life productivity equal to several hundred acres of nearshore coastal habitat. PG&E has partially mitigated for these losses from prior years through payment of an annual in-lieu mitigation fee through the states once-through cooling program; however, that annual fee does not ensure consistency for purposes of the ongoing Coastal Act and CCMP review of the proposed 20-year license renewal. The Coastal Act and CCMP also have policies regarding protection of marine life that are different than those of the federal Clean Water Act referenced on page 3-74. Additionally, the supposed acclimation of marine life to an artificially-induced ecosystem does not allow for an accurate portrayal of likely impacts, and importantly, of the benefits that would accrue under a no project scenario. The Coastal Commission will be conducting its independent review of the expected marine life impacts resulting from license renewal.

Further, and as noted above, the expected update of Diablo Canyons NPDES permit is likely to include several changes from the current permit, largely due to the changes in the states water quality standards over the past 30+ years since the existing permit was approved. We recommend the Draft Supplement include a description of the likely or potential changes resulting from those modified water quality standards, such as changes to effluent limitations, thermal plume modeling, or others.

Other Issue Areas: We understand that PG&E is considering requesting that the NRC approve a reduction in the security zone around the facility, which now consists of almost 12,000 acres along several miles of shoreline north and south of the current Owner Controlled Area. We recommend the NRC include in a subsequent document an analysis of the effects of such a reduction on coastal resources, including the effects on public access to the shoreline.

Coastal Commission comments on Draft Supplement 62 December 16, 2024 5

Closing Thank you for your attention to these comments. If you have questions or would like more information about them, please contact me at tom.luster@coastal.ca.gov.

Sincerely, Tom Luster Senior Environmental Scientist Energy, Ocean Resources, and Federal Consistency

Attachment:

December 16, 2024 technical memorandum on seismic issues at Diablo Canyon

STATE OF CALIFORNIA - CALIFORNIA NATURAL RESOURCES AGENCY GAVIN NEWSOM, GOVERNOR CALIFORNIA COASTAL COMMISSION 455 MARKET STREET, SUITE 300 SAN FRANCISCO, CA 94105-2219 VOICE (415) 904-5200 December 13, 2024 TECHNICAL MEMORANDUM To:

Nuclear Regulatory Commission From:

California Coastal Commission Re:

Response to U.S. NRC Report NUREG-1437, Supplement 62, Generic Environmental Impact Statement for License Renewal of Nuclear Plants, Regarding License Renewal of Diablo Canyon Nuclear Power Plant, Units 1 and 2, Draft Report for Comment, dated October 2024.

Location:

San Luis Obispo County, California This technical memorandum focuses on the seismic source characterization aspects of the NRC NUREG-1437, Supplement 62 draft report. In Chapter 3 (Section 3.4.5), the report briefly summarizes the seismic setting and history. That section identifies the Hosgri fault as primary contributor to the Diablo Canyon Power Plant (DCPP) seismic hazard, followed by the San Luis Bay, Los Osos, and Shoreline faults. Though we agree that the current understanding of the seismic hazard at the DCPP indicates that approximate ranking of seismic sources, we wish to draw the NRCs attention to a broader range of concerns regarding Pacific Gas and Electrics recent update to their seismic hazard assessment for the DCPP (PG&E, 2024).

The California Coastal Commission participates in the Independent Peer Review Panel for Seismic Hazard Studies of the Diablo Canyon Nuclear Power Plant (IPRP), a multi-agency panel of seismic hazard specialists from the California Geological Survey, California Coastal Commission, California Energy Commission, California Seismic Safety Commission, California Public Utilities Commission, County of San Luis Obispso, and Governors Office of Emergency Services. In August 2024, the IPRP issued IPRP Report No. 16 (IPRP, 2024) that provided peer review comments regarding the seismic source characterization summarized in the PG&E (2024) report. The report included a request that PG&E respond within 60 days; so far, there has been no written response from PG&E. The topics addressed in the IPRP report include the Hosgri fault slip rate, fault geometry models and characterization of seismic hazard at the Irish Hills, relevant data not included in the PG&E (2024) report, and ground motions. This memorandum summarizes those comments in the hope that the NRC will understand the full range of our concerns about the PG&E (2024) report. The full IPRP report is available at https://www.cpuc.ca.gov/-/media/cpuc-website/divisions/energy-division/documents/electric-costs/diablo-canyon-independent-peer-review-panel-reports/iprp-report-16-pge-dcsa-update-review.pdf.

2 Hosgri Fault Slip Rate PG&E (2024) proposes a slip rate model for the Hosgri fault that gives varied weights to four different slip rate sites. It is our opinion that only one of these sites (the Cross Hosgri Slope, CHS) provides high quality slip rate data that are relevant to the current hazard model for the DCPP. The CHS site is an offshore paleoshoreline dated at approximately 12 ka with a well-defined fault offset. Those data yield a slip rate of 2.6 +/- 0.8 mm/yr with a high degree of confidence. The results of the CHS study were published in peer-reviewed journal articles (Johnson, et al., 2014; Kleusner, et al., 2023; Medri, et al., 2023).

The three other slip rate sites used by PG&E (2024) are the San Simeon, Estero Bay, and Point Sal sites. The detailed summary of data for these sites comes from previous technical reports by PG&E (2014, 2015). The slip rate from the San Simeon site comes from offset of an onshore marine terrace that is dated to marine isotope stage 7 (~210ka) based on correlation that was not independently verified with other dating methods. This marine terrace has a sinuous rather than straight-line character that leads to large uncertainties in the offset measurement. The preferred slip rate reported for the San Simeon site is 1.8 mm/yr.

The offset paleo-channels at the offshore Estero Bay site are bracketed by unconformities that lack angular discordance and, thus, might not be unconformities. The dating of these channels relies on correlation of the bracketing unconformities with unconformities of known age. The mean age of the offset channel is thought to be 840 +690/-

250 ka, indicating very large uncertainties. The measured channel offsets also have large uncertainties. The slip rate estimates for the Estero Bay site range from 0.39 to 4.71 mm/yr with a preferred value of 1.75 - 1.90 mm/yr.

The offshore Point Sal site has a variety of offset paleo-channels that are difficult to match across the fault, but the researchers chose one channel that they concluded is offset 550 to 700m (preferred value of 600-650m) and another channel that appears to be offset 500-550m. They estimated the ages of the channels based on correlation of the bracketing unconformities with sea level low stands which yields three possible ages, 138 ka, 342 ka, and 1.4 Ma. The researchers identified 342 ka as the preferred age. These drastically different age estimates yield three very different slip rates (4.35-4.71 mm/yr, 1.75-1.90 mm/yr, and 0.43-0.46 mm/yr) with a preferred value of 1.8 +/- 0.4 mm/yr.

Clearly, the San Simeon, Estero Bay, and Point Sal studies have very large uncertainties and yield slip rate data for the Hosgri fault that partly reflects fault slip hundreds of thousands of years ago. Those studies were not published in a peer-reviewed journal.

The Holocene slip rate data from the CHS site reaches a much higher scientific standard.

Since fault slip rates can and do change over time, a Holocene slip rate is more representative of the current slip on the fault than a slip rate that may reflect a different phase in the evolution of the fault. Prior to the offshore research that recognized and characterized the CHS site, the other three sites provided the only available slip rate data for the Hosgri fault. With the publication of the CHS data, the understanding of the Hosgri fault has taken a big step forward, and the lower quality sites are no longer useful. Therefore, the IPRP recommended that PG&E give 100% weight to the CHS site in their seismic hazard model for the Hosgri fault.

3 Irish Hills The DCPP is located at the west end of the west-northwest striking uplift known as the Irish Hills. This uplift is bounded on the north by the Los Osos fault and on the south by a set of faults known as the South Boundary Zone (including the San Luis Bay, Wilmar Avenue, and San Luis Range faults). PG&E (2015) identified three fault block geometry models for the faults that bound the Irish Hills. The first is the Outward-Vergent (OV) model that posits oblique reverse-dextral slip on the Los Osos fault with uplift of the Irish Hills the result of reverse slip accompanied by strike slip motion on both the south-dipping Los Osos fault and the north-dipping San Luis Bay fault. The Southwest-Vergent (SW) model calls for uplift of the Irish Hills by thrust/reverse slip on the San Luis Bay fault and other Southwest Boundary Zone faults that dip approximately 45° northeast. The Northeast Vergent (NE) model calls for uplift of the Irish Hills by northeast-vergent reverse slip on the Los Osos fault that dips approximately 50° to the southwest. PG&E (2015) gave the OV and SW fault block geometry models 40% weight (each) and the NE model 20% weight in their logic tree. The PG&E (2024) report restated the fault block geometry models from the PG&E (2015) report, because new data were not available to improve on these initial hypotheses.

Currently, the fault geometry model for the Irish Hills remains unresolved and warrants further investigation to characterize these seismic sources. Based on the demonstrated success of offshore low-energy seismic reflection methods, the IPRP recommended additional investigation of the faults that bound the Irish Hills in the offshore setting. In fact, preliminary data from offshore studies (Watt, et al., 2015) show that the offshore Los Osos fault is a broad zone that includes vertical faults and flower structures, indicating a possible strike slip fault geometry rather than the hypothesized reverse/thrust fault geometry. More detailed offshore investigation using low-energy seismic reflection methods may provide a better understanding of fault geometries and could identify offset features, such as paleo-shorelines, that could improve slip rate estimates for these faults.

The Los Osos fault seems particularly promising, based on the results of initial studies.

Additional onshore investigation is also needed to evaluate the potential contribution of the faults that bound the Irish Hills.

New Data Not Addressed in the PGE (2024) Report The IPRP identified two relevant studies that were not discussed in the PG&E (2024) report, and this raises a question about the completeness of PG&Es review of available data. A study by McGregor and Onderdonk (2021) concluded that the Casmalia fault (located approximately 27 km south of the DCPP) is a thrust fault with a slip rate of 5.6 to 6.7 mm/yr. This slip rate is an order of magnitude greater than the 0.5 mm/yr value used by PG&E (2015) in their seismic source characterization. Given the proximity of the Casmalia fault to the DCPP, the new slip rate data has implications for seismic hazard that should have been addressed in the PG&E (2024) report. These new data have implications for regional deformation models, because the nearby Casmalia Hills may represent an analog to the Irish Hills in addition to a seismic source with potential kinematic connections to the Hosgri fault and other faults in the vicinity of DCPP.

A NRC-commissioned study (CNWRA, 2016) of offshore seismic reflection data reported that Hosgri fault slip rates have increased during the past million years. This suggests that rates older than Holocene are not representative of the current seismic hazard.

4 Clearly, that study should have been considered in the PG&E (2024) report, because the study results could inform the weighting of Hosgri fault slip rates.

Based on the discovery of the two above studies that were not included in PG&E (2024) report, the IPRP expressed concern that other studies might have been missed and requested that PG&E conduct a comprehensive review that includes all fault studies in the region since the previous assessment (PG&E, 2015). That review should address the implications for the seismic hazard at the DCPP, including newly developed slip rates on faults in the region that may inform deformation rates of faults in the vicinity of Diablo Canyon.

Ground Motions The IPRP found that the methods used to estimate ground motions for the DCPP site appear appropriate for the current seismic source characterization, and PG&Es evaluation of new data and new ground motion models appears adequate. However, the results of site-specific ground motion hazard should be recalculated once changes are made to the seismic source characterization inputs.

The IPRP encouraged efforts to improve the characterization of site conditions in terms of VS profile and kappa estimate. They also suggested the use of more traditional site response models to supplement existing analyses and encouraged continued efforts to reduce uncertainty in empirical site factors, including further improving the non-ergodic ground motion modeling approach and data. In addition, they expressed a need for updated analysis of seismic hazard model inputs ranking sensitivity of ground motion hazards to uncertainties in revised input parameters.

Conclusions Based on review of the PG&E (2024) report, the IPRP concluded that PG&E should reconsider their weighting of slip rates for the Hosgri fault and adopt a 100% weighting for the CHS slip rate. Significant uncertainties remain regarding the characterization of faults surrounding the Irish Hills, and additional investigation is needed to better understand both fault geometry and seismic hazard. PG&E should review all fault studies within the region surrounding the DCPP and include the data from those studies in their evaluation of seismic hazard. Though PG&E has utilized appropriate methods to estimate ground motions at the DCPP site, additional improvements could be made, and ground motion estimates should be recalculated in response to changes in seismic source characterization.

5 References CNWRA, 2016. Independent Evaluation of the Hosgri Fault Slip Rate based on a Structural Analysis of the Pull-Apart Basin Linking the Hosgri and San Simeon Fault Systems, prepared for U.S. Nuclear Regulatory Commission, Contract No. NRC-HQ;50-14-E-0001, Center for Nuclear Waste Regulatory Analyses, San Antonio, Texas, report dated August 5, 2016, 40 pages.

Independent Peer Review Panel (IPRP), 2024, Initial Review of the PG&E Updated Seismic Assessment, February 2024 by the Independent Peer Review Panel for Seismic Hazard Studies of the Diablo Canyon Nuclear Power Plant, Report No. 16, report dated August 26, 2024, 44 pages.

Johnson, S. Y., S. R. Hartwell, and P. Dartnell. 2014. "Offset of latest Pleistocene shoreface reveals slip rate on the hosgri strike-slip fault, offshore central California." Bulletin of the Seismological Society of America, v. 104, p. 1650-1662.

Kluesner, J.W., Johnson, S.Y., Nishenko,S.P., Medri, E., Simms, A.R., Greene, H.G., Gray, H.J.,Mahan, S.A., Padgett, J.S., Krolczyk, E.T., Brothers,D.S., and Conrad, J.E. 2023.

"High-resolution geophysical and geochronological analysis of a relict shoreface deposit offshore central California: Implications for slip rate along the Hosgri fault." Geosphere v.19, no. 6, p.1788-1811.

Medri, E., Simms, A.R., Kluesner, J., Johnson, S.Y., Nishenko, S.P., Greene, H.G., and Conrad, J.E., 2022, Subaqueous clinoforms created by sandy wave-supported gravity flows: Lessons from the central California shelf: Marine Geology, v. 456, https://doi.org/10.1016/j.margeo.2022.106977.

McGregor, I.S., and Onderdonk, N.W., 2021, Late Pleistocene rates of rock uplift and faulting at the boundary between the southern Coast Ranges and the western Transverse Ranges in California from reconstruction and luminescence dating of the Orcutt Formation: Geosphere, v. 17, no. 3, p. 932-956, https://doi.org /10.1130/GES02274.1.

Pacific Gas and Electric Company (PG&E), 2014, Chapter 3, Offshore low-energy seismic reflection studies in Estero Bay, San Luis Bay, and Point Sal Areas, PG&E Technical Report GEO. DCPP.TR.14.02, 178 pages.

Pacific Gas and Electric Company (PG&E), 2015, Seismic Source Characterization for the Diablo Canyon Power Plant, San Luis Obispo County, California, technical report, dated March 2015, 652 pages.

Pacific Gas and Electric Company (PG&E), 2024, Diablo Canyon Updated Seismic Assessment, Response to Senate Bill 841, technical report, dated February 1, 2024, 392 pages.

Watt, J. T., Johnson, S. Y., Hartnell, S. R, and Roberts, M., 2015, Offshore geology and Geomorphology from Point Pedras Blancas to Pismo Beach, San Luis Obispo County, California: U. S. Geological Survey Scientific Investigations Map 3327.