Proposed Oakland A’s Howard Terminal ballpark and condo site hit by liquefaction event during 1989 earthquake. Report fails to mention event.
The proposed Oakland A’s Howard Terminal ballpark and condominium site at the Port of Oakland suffered an “appreciable” liquefaction event, or land sinking, equaling a maximum of 11.8 inches during the 1989 Loma Prieta earthquake, according to a U.S. Geological Survey (USGS) report.
The report, entitled “Soil Liquefaction In The East Bay During The Earthquake”, summarized the geological conditions and noted that damage had occurred at the Port of Oakland:
“Uncompacted artificial-fill deposits on the east side of San Francisco Bay underwent moderate to severe levels of soil liquefaction during the 1989 Loma Prieta earthquake. Typical of all these sites, which represent occurrences of liquefaction-induced damage farthest from the rupture zone, are low cone-penetration-test (CPT) and standard-penetration-test (SPT) resistances in zones of cohesionless silty and sandy hydraulic fill… The most noteworthy damage occurred at the Port of Richmond, San Francisco-Oakland Bay Bridge Toll Plaza, Port of Oakland, Alameda Naval Air Station, Bay Farm Island, and Oakland International Airport.”
The segment in this report that focused on the Port of Oakland cited liquefaction damage at several marine terminals including “appreciable settlements “at Howard Terminal which was quantified at a maximum of 30 centimeters or 11.8 inches:
“Liquefaction of the hydraulic fill caused appreciable settlements (max 30 cm) over large areas of the Howard and APL (American President Lines) Terminals. Although pavement was damaged at the edges of the wharves and in the inboard container yards, there was no apparent damage to piles or adverse movements of the crane rails.”
Oakland Geological Conditions Report Omits 1989 Liquefaction Event But Warns Of Danger
The recently released City of Oakland Environmental Impact Report of the proposed Howard Terminal ballpark and condominium site includes a “Geotechnical Conditions Report” produced in 2019 by the firm ENGEO which is entitled “Oakland Athletics Ballpark Development Howard Terminal Oakland, California Preliminary Geotechnical Exploration Report.”
The ENGEO report was addressed to Mr. Noah Rosen Manager, Project Development Oakland Athletics 7000 Coliseum Way Oakland, CA 94621 and dated April 19, 2019.
The ENGEO report does not mention the 1989 liquefaction event at Howard Terminal, but acknowledges the site “may be susceptible to liquefaction” and that some areas on the site “will likely liquefy during strong ground shaking” as it explains:
“The site is located within a State of California Seismic Hazard Zone (CGS, 2006) for areas that may be susceptible to liquefaction …
Soil liquefaction results from loss of strength during cyclic loading, such as imposed by earthquakes. The soil most susceptible to liquefaction is clean, loose, saturated, uniformly graded fine sand below the groundwater table. Empirical evidence indicates that loose silty sand is also potentially liquefiable. When seismic ground shaking occurs, the soil is subjected to cyclic shear stresses that can cause excess hydrostatic pressures to develop. If excess hydrostatic pressures exceed the effective confining stress from the overlying soil, it is said to have liquefied, and if the sand consolidates or vents to the surface during and following liquefaction, ground settlement and surface deformation may occur.
The hydraulically placed fill in Zone 1, much of the non-engineered fill in Zone 2 and some of the naturally deposited loose sand near the top of the Merritt Sand layer will likely liquefy during strong ground shaking in a major earthquake event associated with nearby active faults.”
A source familiar with the due diligence required for the geological analysis told AJOT: “The omission of the USGS report needs to be recognized by the consultant and an evaluation made as to whether additional data will be required.”
ENGEO Response
Jeff Fippin, a professional engineer and one of the authors of the ENGEO report, admitted to AJOT that the USGS report and the 1989 liquefaction incident at Howard Terminal were not referenced in the geological analysis of the Howard Terminal site:
“While the 1989 event and the USGS report may not have been referenced in the (ENGEO) geological report, the threat of liquefaction at Howard Terminal is a real one and one that we know occurred in 1989 and that could occur again. As a result, we have proposed mitigation measures including significant ground improvements that have worked in the past and are being deployed at the WETA (Water Emergency Transportation Authority) ferry terminal in Alameda (across the Oakland Estuary from Howard Terminal) and at Treasure Island (which lies between Oakland and San Francisco). We are proposing similar measures for the Howard Terminal site. While it is true that we have used the word ‘potential’ in our report, it is because we engineers do not like to make guarantees … but it is not because we are not mindful of the liquefaction threat at Howard Terminal.”
Fippin also said that the Howard Terminal site covers an area of contamination that is currently capped by the existing Howard Terminal pavement surface. He does not believe that the contaminants will spill out in the event of a liquefaction event: “The contamination area is located in the Zone 2 area of the site behind a 20-foot quay wall. The contamination dates back to a time before Howard Terminal became a container terminal. The threat of liquefaction is believed to be less in the Zone 2 area located behind the quay wall.”
ENGEO Proposed Mitigations
The ENGEO report proposes the following mitigation measures to address the liquefaction problems at Zones 1 and Zone 2 within the Howard Terminal site:
The ENGEO report warns these measures are essential:
- “Based on local experience and our understanding of the composition and depth of the hydraulically placed fill, we anticipate Direct Power Compaction (DPC) can be used in Zone 1A to densify the fill. DPC is a vibro-compaction technique that densifies loose sandy soil by a combination of vibration and compaction. We recommend the DPC compaction be followed by tamping to compact the upper 5 to 8 feet of sandy soil. Other ground improvement methods are likely feasible in this zone; however, our experience indicates DPC is likely the most efficient for treating the entire thickness of fill. Because the liquefaction hazard in this zone is substantial and the potential settlement is large even at low return periods, we recommend performing ground improvement in this zone regardless of the building foundations used…
- The fill placement in Zone 1B was performed during 1995…. the sandy fill in this zone was compacted to some degree, though no specifications or records of placement were available at the time of preparing this report. Our analysis results indicate up to 5 inches of settlement in the fill; therefore, we recommend using Direct Power Compaction (DPC) to densify the loose sandy fill. We also recommend the DPC compaction to be followed by tamping to compact the upper 5 to 8 feet of sandy soil …
- In Zone 2, the fill contains more silt and clay compared to Zone 1. In Zone 2, liquefaction mitigation may not be necessary if the buildings are supported on deep foundations obtaining all their support in the soil below the fill and YBM (Young Bay Mud). However, if shallow foundations are utilized ground improvement will likely be necessary to mitigate liquefaction settlement. Additionally, ground improvement can be used in areas supported by pile foundations (such as the ballpark structures) to increase the lateral capacity of the foundation system. Due to the nature of the fill, Deep Dynamic Compaction (DDC) or Rapid Impact Compaction (RIC) are likely the most feasible methods to densify the non-engineered fill.”
“Without mitigation, based on the thickness of the hydraulically placed fill in Zone 1, settlement in this zone could be over 8 inches at a building code Maximum Considered Earthquake level earthquake. In Zone 2, where the liquefiable soil is considerably thinner and has higher fines content, the settlement is about 2½ to 5 inches. Considerable settlement is likely in Zone 1 even at significantly lower levels of seismic shaking.”
According to the City of Oakland, the Oakland A’s Howard Terminal project proposes:
- Construction of an approximately 35,000-person capacity Major League Baseball park for the Oakland Athletics.
- Up to 1.77 million square feet of commercial development,
- Up to 3,000 residential dwelling units,
- A new hotel with approximately 400 rooms, and
- A new performance venue with a capacity of approximately 3,500 individuals.
