HomeMy WebLinkAbout1989-356
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RESOLUTION NO. 89-356
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RESOLUTION OF THE CITY OF SAN BERNARDINO ADOPTING
3 PROCEDURES AND GUIDELINES FOR LIQUEFACTION INVESTIGATIONS AND
REPORTS REQUIRED BY CHAPTER 15.08 OF THE SAN BERNARDINO MUNICIPAL
4 CODE; AND RESCINDING RESOLUTION NO. 82-345.
5 BE IT RESOLVED BY THE MAYOR AND COMMON COUNCIL OF THE CITY
OF SAN BERNARDINO AS FOLLOWS:
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SECTION 1. Administrative Procedures/Guidelines for
7 Liquefaction Investigations and Reports.
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In accordance with Chapter 15.08 of San Bernardino
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Municipal Code.
The Director of Public Works/City Engineer has
10 established the following procedures/guidelines for liquefaction
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11 investigations and reports.
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SECTION 2. The Investigation.
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Purpose.
The investigation shall be designed and
A.
carried out to determine the potential for liquefaction.
For
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15 complex, essential structures, the investigation shall be as
thorough as current technology will permit.
Investigations may
17 also require the expertise of a registered geologist, or
18 registered engineering geologist, since both geologic/seismic
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19 elements and quantitative materials testing will be involved.
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B.
Site investigation.
1.
Seismic factors.
The history of earthquake
activity and recurrence intervals of damaging earthquakes
shall be discussed.
A design earthquake shall be
postulated, with a best estimate of the following
characteristics as they will be experienced at the site:
a.
Richter magnitude.
b.
Maximum Probable Rock Acceleration from
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various faults, (as shown in the Seismic Element
of the General Plan) that produces the highest
value.
c.
Time (duration) of strong shaking.
d.
Dominant frequencies of seismic spectra.
e.
In no case shall the rock acceleration be
less than the amount indicated on the map in the
Seismic Element of the General Plan entitled:
'Maximum Credible Rock Acceleration from
Earthquakes.'
2. Hydrologic conditions.
The historical record of
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12 depths to the ground water table (or saturated conditions) shall
be determined for the site from City records.
The depth to
14 ground water used in the analysis, as determined by borings,
15 shall be stated, but design will be based on a level no less than
16 ten (10) feet.
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3. Subsurface Investigation.
Borings shall be used to
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determine the necessary subsurface information.
They should
19 extend to a minimum depth of fifty (50) feet and be spaced across
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20 the site so that significant variations in subsurface conditions
22 be:
will be defined.
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Examples of significant subsurface data would
a.
drilling rate,
b.
standard penetration test at every five (5) feet
from surface ASTM No. D 1586-67,
c.
classification, definition, and depth of soils,
d.
general stratigraphy.
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For essential projects, more subsurface information
2 utilizing pits, trenches and geophysical investigations may be
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They allow direct observation of the undisturbed
necessary.
4 vertical section so that evidence of liquefaction such as sand
5 boils, sand dikes, or chaotic disturbance of the soil or sediment
6 can be viewed. Also, horizontal and vertical permeability can be
7 better estimated from a view of the undisturbed layering.
8 Furthermore, the ancient sedimentary environment of the site can
9 be interpreted from the trench of pit walls.
4.
Geophysical Investigation.
Refraction seismic
11 techniques may be useful to define the ground water table, but
12 this indirect method should only be used to confirm or extend
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13 downhole or trench data.
15 The report may be simple or comprehensive, depending upon
SECTION 3. The Report.
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16 the vulnerability of the site to liquefaction and the kinds of
buildings or other structures to be built.
The following topics
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18 should be considered and included if pertinent.
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A. Text
1.
Site location relative to established property
boundaries.
2.
City reference number (CUP, ROP, Tract No., etc.)
3.
Purpose and scope of investigation.
4.
Design earthquake parameters (discussed above).
5.
Description of kind and location of proposed
construction.
6.
Procedures and techniques used in the
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investigation.
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Detailed description of subsurface conditions and
B. Conclusions and Recommendations.
results of quantitative testing.
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1.
Identify the location and distribution of areas
vulnerable to liquefaction and estimate the depth of
zones of possible failure due to liquefaction.
2.
Identify critical parameters of the design
earthquake:
fault, magnitude, accelerations,
duration, frequency, etc.
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Identify procedures for reducing hazard of
liquefaction.
a.
geotechnical.
b. structural.
C. Documentation of Report.
3.
1.
Include index map showing location of site.
2.
Include site plan which shall display:
a.
topography (if available);
b.
proposed building location;
c.
locations of borings, wells, trenches;
d.
surface geological features.
trenches.
Include logs of borings (with blow counts), wells
4.
Include sample descriptions and locations.
5.
Include sample analysis and tests, based upon the
penetration analysis developed by Dr. Bolton Seed, or
other approved method.
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Include graphs and charts, as needed to
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demonstrate liquefaction potential.
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Include description of analytical techniques
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used.
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Include signatures and license numbers of
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Registered Civil Engineers responsible for the report,
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and any Registered Geologists that assisted in the
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preparation.
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9. Include a list of references utilized in report.
10. List final recommendations with references to
conclusions.
SECTION 4. Submittal.
13 Two copies of the required Liquefaction Report and
14 Mitigation Measures shall be submitted to the Director of Public
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15 Works/City Engineer and approved prior to issuance of grading and
building permits.
If the Liquefaction Report and Mitigation
17 Measures are approved by the Director of Public Works/City
18 Engineer, a copy will be forwarded to the Director of Building
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20 structural plans shall contain a statement that the building has
and Safety for reference in checking structural plans.
The
21 been designed in accordance with the Mitigation Measures
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22 contained in the Liquefaction Report.
24 submitted to the Director of Public Works/City Engineer are
If the Liquefaction Report and Mitigation Measures
25 determined to be unacceptable, the interested party may appeal
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this decision to the Mayor and Council.
No permits will be
27 issued prior to approval by the Director of Public Works/City
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1 Engineer or prior to an appeals decision by the Mayor and Common
2 Council approving the Liquefaction Report and Mitigation
3 Measures.
4 I HEREBY CERTIFY that the foregoing resolution was duly
5 adopted by the Mayor and Common Council of the City of San
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Bernardino at a
regular
meeting thereof, held on the 18th
, 1989, by the following vote, to wit:
Council Members Estrada, Reilly, Flores, Maudsley,
Minor, Pope-Ludlam, }filler
None
None
~Q1/~~
CitY Clerk
The foregoing resolution is hereby approved this
, 1989.
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J .::-w. HO'l comb, Ma;y'or
City of!San~Bernardino
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20 Approved as to
form and legal content:
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day of September
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AYES:
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NAYS:
ABSENT:
Of'O~~
JAMES F. PENMAN,
City Attorney
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BY:~ ?;~
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