Subject: Seismic Hazard Zone Maps for Oakland West Quadrangle
From: Mark Swingle <mswingle(--nospam--at)earthlink.net>
Date: Sun, 02 Jan 2000 16:10:54 -0800
<<The following letter was mailed 29 December 1999
to the two addressees listed below and was sent
by email to the first addressee and the three
copied recipients on 2 January 2000.
It is copied here to the SEAINT list server
for information and feedback.
I would appreciate any comments on the following
29 December 1999
State Mining and Geology Board
801 K Street, MS 24-05
Sacramento, CA 95814
California Department of Conservation,
Division of Mines and Geology
San Francisco Area Office
185 Berry Street
San Francisco, CA 94107
Subject: Seismic Hazard Zone Maps
Public Comment for Oakland West Quadrangle
To Whom It May Concern,
On 30 September 1999 the Seismic Hazard Map for the Oakland West
Quadrangle was released for public comment. By this letter I am
hereby declaring my strongest objection to the publishing of this map
in its current form, based upon the three claims outlined below. I
understand that today is the deadline for comments on this map.
I believe that the tentative map as published is fundamentally
flawed, for the reasons outlined below. The map identifies large
areas as being within the zone of hazard due to liquefaction, but I
believe that much of this area poses little risk to the public due to
As I understand the underlying law, this map will become official
several months after this deadline, with consideration given to
public comments on the proposed map.
I hereby claim the following:
1. Inadequate public notice was given regarding this map
because the required public hearing did not take place in the local
2. The criteria used for determining whether a particular
area is to be included in the map as a zone of potential liquefaction
does not comply with the governing code, and therefore poses an undue
burden on the property owners of the area.
3. The particular area in the vicinity of the intersection
of 51st Street and Telegraph Avenue, Oakland, is well known to have
little or no liquefaction risk, yet was included in the map as such
Regarding Item 1:
This is now the end of the 90-day period for public comment, yet no
public hearing took place in the vicinity that could have given the
public and their local representatives the opportunity to comment on
the content of the proposed maps. This public hearing is required by
Section 3723, Article 10 (Seismic Hazards Mapping), Title 24, C.C.R.
states in part as follows:
"3723. Review of Preliminary Seismic Hazard Zones Maps.
(a) The Mining and Geology Board shall provide an opportunity for
receipt of public comments and recommendations during the 90-day
period for review of preliminary seismic hazard zone maps provided by
the Public Resources Code Section 2696. At least one public hearing
shall be scheduled for that purpose."
It is essential that this hearing take place in the local area
affected, and that the public comment period be extended.
Regarding Item 2:
The underlying law specifies that historic occurrences of
liquefaction be considered. I have no quarrel with that.
However, the underlying law also specifies that geotechnical as well
as geological and ground water conditions be considered. Only
geological and ground water conditions are considered in the
criteria. Consideration of geotechnical criteria such as boring
logs, Standard Penetration Tests (SPT), and Cone Penetration Tests
(CPT), where available, is essential in order to comply with the law.
Section 3722, Article 10 (Seismic Hazards Mapping), Title 24, C.C.R.
states in part as follows:
"3722. Requirements for Mapping Seismic Hazard Zones.
... (2) Liquefaction hazard zones shall be delineated as areas where
historic occurrence of liquefaction, or local geological,
geotechnical and ground water conditions indicate a potential for
permanent ground displacements such that mitigation as defined in
Public Resources Code Section 2693(c) would be required."
There have been numerous geotechnical reports prepared for specific
sites within the region that has been tentatively designated as
hazardous. These reports routinely assess liquefaction risk as a
part of the scope of the report.
The criteria should include review of recently-prepared geotechnical
reports throughout the vicinity, before an area is designated as
Regarding Item 3:
I am familiar with the soil in the area of the intersection of 51st
Street and Telegraph Avenue, Oakland. I have also reviewed several
geotechnical reports prepared for recent new development in the
area. None of the reports indicated the potential for liquefaction
was sufficient to require mitigation.
I am aware of no new development within a 1-mile radius of this
intersection where mitigation of potential earthquake-induced
liquefaction was recommended or implemented. This includes extensive
retrofit to the existing Route 24 elevated structure by CalTrans.
Typical mitigation measures include deep foundations, densification
of the liquefiable soil, or removal of the liquefiable soil, among
others. I am aware of no new development in the area where this was
Most of this area was apparently designated hazardous simply due to
the age of the soil, despite the lack of a saturated, loose layer of
sand within the upper 50 feet of soil.
I believe that the process, criteria, and result of the effort put
forth to produce this map are fundamentally flawed for the reasons
The potential effects of the official publication of this map include
a significant decline in the property values of the affected area.
This is because the property disclosure requirements will create a
situation where potential buyers may be "scared off", when in fact
little hazard exists.
This would have a negative effect on the local citizens' net worth
and the local governments' tax base. I believe that this negative
effect may far exceed the minimal benefits. Since most major new
developments are already required to have a geotechnical report, the
benefits of this "stigma" are
Mark T. Swingle, S.E.
copies to: Calvin Wong, Building Official, City of Oakland
Jane Brunner, Oakland City Council, District 1
Jerry Brown, Mayor, City of Oakland