HomeMy WebLinkAboutAdmin Order 58-02-25-F
ADMINISTRATIVE ORDER NO. 58-02-25-F
of the
City Manager pro tern of the City of Eugene
ADOPTION OF STANDARDS FOR GEOLOGICAL AND GEOTECHNICAL
ANALYSIS ADMINISTRATIVE RULE R-9.6710.
The City Manager pro tern of the City of Eugene finds as follows:
A. Section 2.019 of the Eugene Code, 1971 (EC) authorizes the City Manager to adopt
rules for administration and implementation of any provisions of that Code. Some provisions ofEC
Chapter 9 that became effective on June 1, 2002 require the submission of a geological and
geotechnical analysis. The analysis is intended to ensure that public and private facilities in
developments in areas of known or potential unstable soil conditions are located, designed and
constructed in a manner that provides for the public health, safety and welfare. Those EC provisions
set forth the categories and applicability of three different categories of geological and geotechnical
analysis, and provide for specific exemptions.
B. EC 9.6710(2) provides that geological and geotechnical analyses shall be prepared
in a manner that conforms to the standards, procedures and content in the Standards for Geological
and Geotechnical Analysis adopted by the City Manager in the manner provided in EC 2.019.
C. In accordance with the procedures set forth therein, on September 5,2002, the City
Manager Pro Tern issued Administrative Order No. 58-02-25 proposing the adoption of Standards
for Geological and Geotechnical Analysis Administrative Rule R-9 .6710 as proposed therein, in
order to assure that soil investigations are implemented in a manner that is in compliance with the
newly adopted provisions of the Eugene Code, 1971. Notice was provided to the Mayor and City
Councilors, posted at City Hall II (Public Works), 858 Pearl Street, Public Works Engineering, 244
E. Broadway, the Permit and Information Center, and the Eugene Public Library, on September 5,
2002, published in the Register Guard, a newspaper of general circulation within the City for five
consecutive days, to wit, September 9, 10, 11, 12, and 13,2002, and made available for inspection
by interested persons at the offices of the City Engineer and Engineering Development Review
Manager, 858 Pearl Street, Eugene, OR 97401 during normal business hours (8:00 a.m. to 5:00 p.m.,
Monday through Friday, exclusive of holidays).
D. The notice provided that interested persons could submit written comments thereon
for a period of thirty (30) days from the first date of publication and posting. Written comments
were received from Troy Hull, Charles R. Lane, David Holt, and Andrew Goodell of PSI
Engineering Consulting Testing; L. Radley Squire, P.E. Consultant; Gunnar Schiedler ofGeoScienc,
Inc.; H. Stanley Kelsay, David Driscoll, Dwight Hardin, and Michael W. Reed ofGRI Geotechnical
& Environmental Consultants, to which I make the following findings:
Comment 1: All references to "Geotechnical Engineer" should be changed to "Qualified
Registered Professional." All references to "expansive clays" should be
changed to "expansive soils."
Finding:
These changes have been made.
Comment 2: R-9.6710-A. Verify that the terms "complex project" and "design area" are
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Finding:
used in the Administrative Rule and if not used, remove the terms from
Section R-9.6710-A.
The term "complex project" is not used in the Administrative Rule and has
been removed from Section R-9.6710-A. The term "design area" is used in
the Rule.
Comment 3: R-9.6710-A. Design Area: Clarify the intent of the definition that states "and
may be randomly distributed throughout the development site."
Finding:
The definition has been modified. Development sites may have multiple soil
types randomly distributed throughout the site with similar design constraints.
Evaluation of the design criteria for the entire site is required.
Comment 4: R-9.6710-A. Engineering Properties of Soil and Rock: the proposed
Administrative Rule does not provide the quantitative standard method to
determine erodibility.
Finding:
The professional is responsible for providing quantitative measures and
identifYing the standard by which they made the determination. Design
professionals are encouraged to maximize their data collection according to
the needs of the project, i.e. an erodibility measure that is necessary for
erosion prevention permit application. No change is being made to this
provision as a result of this comment.
Comment 5: R-9.6710-A. Engineering Properties of Soil and Rock: Void ratio is an index
property not an engineering property. Recommendation to use Terzaghi,
Peck and Mesri definition from "Soil Mechanics in Engineering Practice", 3rd
Ed.
Finding:
Void ratio has been removed from the list of engineering properties and
added to the list of significant index properties. The definition for index
properties provided in the Administrative Rules is consistent with Terzaghi,
Peck and Mesri's definition.
Comment 6: R-9.6710-A. Expansive Soil: Delete reference to "excessive" expansion and
shrinking.
Finding:
Deletion made.
Comment 7: R-9.6710-A. Qualified Registered Professional: Recommended alternative
definitions by a number of people submitting comments.
Finding:
EC 9.6710(2) establishes that the geological and geotechnical analysis can be
prepared by an Oregon licensed Engineering Geologist or an Oregon licensed
Civil Engineer with geotechnical experience; the Rule describes these two
professionals under the general term "Qualified Registered ProfessionaL"
The Rule cannot alter the code provisions establishing who is allowed to
prepare an analysis. No change is being made to this provision as a result of
these comments.
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Comment 8: R-9 .671 O-A. The term Representative Sample should be Representative
Disturbed Sample. The term Soil Disturbance should be Site Disturbance.
Finding:
The "Representative Sample" term has been changed. The definition of "Soil
Disturbance" was clarified, but the term itselfis used in the Code and was not
changed.
Comment 9: General word smithing comments and suggestions regarding Sections R-
9.6710-B, R-9.6710-C and R-9.6710-D.
Finding:
These sections recite, verbatim, code language and cannot be changed
without an ordinance amending the code. No change is being made to this
provision as a result of these comments.
Comment 10: R-9.6710-F 4.2. How can a Qualified Registered Professional fully address
groundwater elevations and the presence of expansive soils when no
subsurface investigation is performed for a Levell investigation?
Finding:
R-9.6710-F 4.2 has been deleted.
Comment 11: R-9.6710-H 1.4. Terms of timing, extent, and mechanics are applicable
mostly to slope movements. The sentence should end after the word "site."
Finding:
R-9.6710-H 1.4 has been changed.
Comment 12: R-9.6710-H 2.3. Engineering properties of Soil. This section repeats
information given in Section R-9.6710-A.
Finding:
Changes have been made to eliminate the repetition.
Comment 13: R-9.6710-H 3.8.1. The intent of this section is not clear and it should be
removed from the proposed Administrative Rule.
Finding:
R-9.6710-H 3.8.1 has been deleted.
Comment 14: R-9.6710-J - Alternate Methods of Investigations. The approval process for
an alternate method of investigation will likely be time consuming and the
basis for approval is unclear.
Finding:
R-9.6710-J.3 has been changed to require that the City issue a decision on a
request for deviation within 30 days of receipt of the written request. The
Rules cannot establish a standard basis for approval because the nature of the
potential alternate method is unknown. Approval of proposed alternate
methods of investigation will be on a case by case basis. R-9.6710-J.3.1,
however, has been changed to provide additional detail regarding what the
alternate investigation method must include.
Comment 15: R-9.671 O-J. Design recommendations for structures and construction should
be observed by a Registered Professional Engineer. If geology is an issue, the
Registered Professional Engineer may decide to retain a certified Engineering
Geologist to assist.
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Finding:
EC 9.6710(2) establishes that a geological and geotechnical analysis can be
prepared by either an Oregon licensed Engineering Geologist or an Oregon
licensed Civil Engineer with geotechnical experience; the Rule describes
these two professionals under the general term "Qualified Registered
Professional." The Rule cannot establish standards that are more stringent
than the Code. Because the Code permits either an Oregon licensed
Engineering Geologist or an Oregon licensed Civil Engineer to fulfill the
requirements of EC 9.6710, the Rule cannot heighten the Code requirement
by requiring a Registered Professional Engineer to perform certain functions
and by requiring applicants to retain a certified Engineering Geologist to
assist with other functions. No change is being made to this provision as a
result of this comment.
Comment 16: R-9.6710-J. The Administrative Rule is unclear regarding the City's process
for approving other professionals that can verify subsurface conditions during
the construction phase for projects requiring a Level 3 analysis.
Fin din g:
R-9.6710-J has been deleted.
Comment 17: R-9.6710-J. It is unclear who IS allowed to retain the construction
verification service.
Finding:
R-9.6710-J has been deleted.
Comment 18: R-9.6710-J. The Administrative Rule does not provide a procedure for
reporting discrepancies.
Finding:
R-9.6710-J has been deleted.
Comment 19: Will there be a final report required on the earthwork related construction
when it is completed?
Final reports are controlled by the permitting agencies and not a requirement
of land use approval. The Rule is adopted pursuant to EC 9.6710, a land use
approval criteria. It is the professional's responsibility to guide and direct the
developer in what is necessary to obtain a construction permit and construct
a safe and structurally sound facility. Public improvement permitting and
construction procedures are outlined in the City's Public Improvement
Design Standards Manual.
Comment 20: Appendix A. Expressing concern about the minimum number of test holes
recommended in the Appendix.
Finding:
Finding:
Rule R-9.671 0, Appendix A has been revised to reduce the minimum number
of recommended test holes for land divisions.
Comment 21: The establishment of these standards creates a legal precedent for practice in
a field that relies a great deal on experience and judgment, and therefore
markedly increases the potential for litigation involving the practicing
professional and the City of Eugene.
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Finding:
EC 9.6710 establishes the requirement for a geological and geotechnical
analysis and directs the City Manager to adopt administrative rules setting
forth the "standards, procedures and content" of the required analysis.
Further, EC 9.6710(4) establishes the general contents of each of the analysis
levels. Some of the code-established content requires the inclusion of
information that is based on the experience and judgment of the Qualified
Registered Professional, i.e., "recommendations for design and construction
techniques," and "identification of potential problems." The Rule explains,
specifically, what is required by the code, generally. No change is being
made to this provision as a result of this comment.
Comment 22: R-9.6710-A. The proposed Administrative Rule violates Oregon state law
by allowing registered geologists to practice engineering.
Finding:
EC 9.6710(2) establishes that the geological and geotechnical analysis can be
prepared by an Oregon licensed Engineering Geologist or an Oregon licensed
Civil Engineer with geotechnical experience. EC 9.6710(4) establishes the
three categories/levels of analysis and, generally, the content of each level of
analysis. The Rule simply sets forth the acceptable methods to be used for
investigating and reporting the geological and geotechnical site investigations
for levels and consistency of analysis established by the code. A Qualified
Registered Professional must always comply with Oregon Revised Statutes
Chapter 672; neither the Rule or the Code eliminates this state law
requirement. No change is being made to this provision as a result of this
comment.
Comment 23: R-9.6710-G.2.3. There is no analytical method that allows someone to make
reasonable determinations, evaluations, or expectations concerning
consolidation or settlement based on a "visual manual estimate" of the soils.
Finding:
Visual manual estimates represent the professional's observation of the soils
and are the foundation for their decision to complete additional testing to
determine consolidation or settlement risks. No change is being made to this
provision as a result of this comment.
Comment 24: The proposed Administrative Rule develops a standard of practice that will
have legal implications burdensome to both the City and the consulting
community.
Finding:
Eugene Code Section 9.6710 establishes the geological and geotechnical
analysis requirement. Further, EC 9.6710(4) sets forth the three
categories/levels of geological and geotechnical analysis and the general
required contents of each analysis level. Because this comment does not
specifically identify which of the Rule provisions will have potential "legal
implications burdensome" to the City and the Community the comment
cannot be responded to further. No change is being made to the Rule as a
result of this comment.
Comment 25: Is the National Resources Conservation Services soil manual the same as the
Soil Survey for Lane County?
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Finding: Yes.
Comment 26: In order to establish a level plaYing field for Engineering Geologists and
Engineers, would it be reasonable to establish a requirement for similar years
of experience?
Finding:
Engineering Geologists are required to be educated in soils and have field
experience in Engineering principles to qualify to sit for the Certified
Engineering Geologist exam. While Professional Engineers are experienced
in engineering principles there is no requirement that their experience include
soils to sit for the professional exam. The City asks that professional
engineers have 4 years experience in soils to submit geological and
geotechnical reports. No change is being made to this provision as a result
of this comment.
Comment 27: It is not clear what level of analysis would be required for projects that do not
involve land use applications for subdivisions, site reviews and planned unit
developments.
Finding:
Pursuant to EC 9.6710(3), a geological and geotechnical analysis is required
for: (1) proposed tentative planned unit development, site review, and
subdivision application on properties with slopes equal to or greater than 5%;
and (2) developments proposing public improvements. Thus, unless the land
use application proposes to dedicate or construct a public street or alley or the
construction of public drainage systems or public wastewater sewers, no
analysis is required for any other type of land use application except
subdivisions, site reviews and PUDs (with slopes equal to or greater than
5%). No change is being made to the Rule as a result of this comment.
Comment 28: Who will protect the public from risk to life-safety for projects exempted in
R-9.6710-D and constructed on a site that contains geotechnical or geologic
risk? What is the purpose for exempting these types ofprojects?
Finding:
The exemptions set forth at R-9.6710-D were established by ordinance and
are listed in Section 9.6710 of the Eugene Code, 1971. No change is being
made to this provision as a result of this comment.
Comment 29: The City should table consideration of the proposed Administrative Rule, or
work with affected professionals to develop language that is consistent with
state law and current standards of practice.
Finding:
Throughout the drafting of this Rule, the City engaged in an exchange
with design professionals from around Oregon. Further, the City obtained
comparative rules from other agencies that deal with geologic and
geotechnical issues, such as the Oregon Board of Geologist Examiners, the
United States Department of Agriculture, Marion County, the City of Salem,
the City of Gresham, the City of San Diego, California, and the Department
of Geology and Mineral Industry. This Rule has been reviewed by the
Oregon State University Geological Engineering professionals, the Oregon
State Board Examiners of Engineers and Land Surveyors (OSBEELS), the
Oregon State Board of Geologist Examiners (OSBGE), and geological
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advisors. The Rule is not being tabled and no change is being made to the
Rule as a result of this comment.
E. City staff has worked with the development community for several months in
developing the Standards for Geological and Geotechnical Analysis contained herein. After
reviewing the comments received, and making some revisions in response to the comments, staff
recommended that the public be provided an additional opportunity to comment on the rules and
proposed revisions. I concurred with the staffs recommendation, and caused a notice to be
published on January 12,13, 14, 15, and 16,2003 advising that comments would be received thereon
for a period of 15 days from the first publication date, or at a public hearing to be held on January
22, 2003.
F. No written comments were received in response to the notice or at the public hearing
except the following comments from the Law Office of Bill Kloos, PC, which were submitted on
behalf of their client Tom Poage of Poage Engineering & SurveYing, Inc., at the public hearing held
on January 22, 2003, to which I make the following specific findings:
Comment 1: The Standards for Geological and Geotechnical Analysis should be adopted
with pre- and post-adoption notice provided to DLCD.
The City has provided pre-adoption notice to DLCD, and will provide DLCD,
within five-days of adopting the Rule, post-adoption notice.
Comment 2: The Standards for Geological and Geotechnical Analysis should be adopted
by ordinance, not administrative rule.
Finding:
Finding:
This administrative rule implementing the policy set forth in EC 9.6710 is not
a legislative act; rather, it is, by definition, an administrative act. The rule
does not contain criteria beyond those required in Chapter 9. Thus, the City's
enactment of this Rule is consistent with ORS 227.186(2) and need not be
adopted by ordinance. Also, EC Section 9.6710 is an acknowledged land use
regulation (Chapter 9) establishing the requirement for a geological and
geotechnical analysis and directs the City Manager to adopt administrative
rules setting forth the "standards, procedures and content" of the required
analysis. No change is being made as a result of this comment.
Comment 3: The City should consider waiting until the Oregon State Board of Examiners
for Engineering and Land Surveying (OSBEELS) issues its new rules
governing geotechnical analysis and engineer certification before enacting
this Rule so that they are consistent with the state rules.
A group of professional engineers who believe that Certified Engineering
Geologists do not have sufficient training and understanding in engineering
principles to design facilities encouraged OSBEELS to recognize
Geotechnical Engineers and address geotechnical engineering standards. In
contrast, the Oregon State Board of Geologist Examiners (OSBGE) has set
the standards for Geologists and they have adopted guidelines for preparing
engineering geologic reports in Oregon. There is a belief in the geological
field that engineers lack sufficient training in Geology. This difference of
opinions has been an issue put before both Boards for more than three years
and it is uncertain as to when decisions will be made. This rule was sent to
Finding:
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both OSBEELS and OSBGE for their input. OSBEELS did not provide any
comments. Gary Peterson, reviewed the Rule for OSBGE, and provided
some comments. Many of those comments were incorporated into the Rule
before the September 2002 commenting period. Due to the uncertainty of
when OSBEELS and OSBGE will resolve the issue, the City must move
forward to adopt administrative rules, as required by EC 9.6710.
Comment 4: Expressing concern about the qualifications of the persons at the City who
will review the reports. The express professional opinion of a certified
engineer warrants a review under published standards by someone qualified
to understand and comment professionally on the report.
Finding:
The City will not conduct an independent geological or geotechnical
investigation of the proposed development site as a means of"reviewing" and
verifYing the qualified registered professional's opinions set forth in the
submitted analysis. The investigation conducted by the professional and the
professional's opinions set forth in the analysis will be relied upon by the
City during the land use approval process as verification that the site is suited
for the proposed development. Also, the information contained in the
analysis will be used by the City to determine if the applicant has satisfied
code criteria requiring that the proposal not pose a significant risk to public
health and safety (EC Sections 9.4885(4),9.8515(5),9.8320(6)). No change
is being made to the rule as a result of this comment.
Comment 5: More detail should be given regarding Attachment A, i.e., the source.
Finding: Attachment A was provided by the late Joe Spigolon, and adjusted by City
engineering staff to maintain consistency with the City's design and
investigation standards. Attachment A is the minimum level of boring
expected and is used to evaluate whether additional borings are necessary.
The qualified professional is responsible for determining the full level
investigation required to support the proposed development. No change is
being made to the rule as a result of this comment.
Comment 6: There appears to be a conflict between certain requirements for a Level One
and Level Two analysis and the requirements contained in the code. For
example, in section 4 of the Level One analysis, the rule states that if certain
criteria are met, a Level Two analysis should be done. The code says nothing
about going from a Level One to a Level Two analysis, only from a Level one
to a Level Three analysis.
Finding: The Rule has been changed so that the Rule requirements are consistent with
the Code.
Comment 7: The mere presence of "expansive soils" in a Level One analysis requires that
a Level Two analysis be conducted. That requirement goes beyond the code
provisions which provide when a Level Two analysis is to be conducted.
Finding:
The Rule has been changed so that the Rule requirements are consistent with
the Code.
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Comment 8: R-9.6710-J - Construction Verification adds anew level of regulation that is
not contained in the Code.
Finding:
R-9.6710-J has been deleted.
G. Based on the above findings in response to the comments received, and the
recommendation of staff that Rule R-9.6710 be adopted as amended, I find that adoption of the
Standards for Geological and Geotechnical Analysis Administrative Rule R-9.6710 as hereinafter
set forth is necessary in order to provide direction in meeting the requirements of the Eugene Code,
1971, and I hereby adopt the following:
ST ANDARDS FOR GEOLOGICAL AND GEOTECHNICAL ANALYSIS
ADMINISTRATIVE RULE R-9.6710
R-9.6710-A Definitions.
As used in this Rule, the following words and phrases are defined in alphabetical order as
follows:
Design Area: Soil areas within the development site having similar material and
groundwater characteristics, both in physical properties and vertical and horizontal
distribution, such that the engineering design and construction capabilities and constraints
are the same.
Engineering Properties of Soil and Rock: The engineering or physical properties
of soil and rock depend on both the material, or grain, properties and their in-situ, or
undisturbed, texture, packing, particle orientation, and degree of saturation. Shear strength,
compressibility, expansivity, permeability, and erodibility are most often the engineering
properties of interest. The engineering characteristics of an in-situ rock mass most often
focus on discontinuities, such as bedding, shear zones, and fractures. Such features are
described in terms of frequency, attitude, spacing, roughness, bonding quality, and general
continuity.
Expansive Soil: Soils containing expansive clay minerals, such as, but not limited
to, montmorillonite, which expands when subjected to a moisture increase and which shrinks
when subjected to a moisture decrease. Soils identified in the Natural Resources
Conservation Services soil manual as having a high shrink -swell potential shall be
considered expansive soils.
Index Properties of Soil or Rock: The soil material or grain properties of the
material itself, regardless of the in-situ, or undisturbed, texture, packing, orientation, or
degree of saturation. The soil index properties of significance are the properties of the
individual grains or particles, including the distribution of grain sizes, the shape, angularity,
and hardness of individual grains, the amount and type of clay minerals, and the presence and
amount of organics. The rock index properties include color, texture, degree of weathering,
hardness, and geologic origin. The soil/rock index properties are used to indicate, or infer,
potential engineering behavior. The index properties are evaluated to reduce the need for the
more complex and costly engineering (physical) properties tests.
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Intact Character of Rock: In the Eugene/Springfield area, rock units are Tertiary
in age - between 1.64 million years (My) and 35 Myoid. Rock units are classified on the
basis of origin, whether igneous (intrusive or extrusive) sedimentary (marine or terrestrial),
pYroclastic, or metamorphic; geologic name; color and texture (grain size); hardness; degree
of weathering; and if available, degree of fracturing.
Pistol-Butt (on Tree): Also called gun-stocked tree. A curved basal section of
trunk, resulting from down-slope rotation of the base of the tree. Similar in shape to curved
butts on antique side arms.
Qualified Registered Professional: An Oregon Registered Professional Engineer
(per ORS 672.002 to 672.325), who by training, education, and having a minimum of four
years geotechnical experience, is especially qualified to apply the principles of soil
mechanics, rock mechanics, hydraulics, and geological science to planning and evaluating
engineering site investigations, making appropriate quantitative analyses and engineering
design recommendations for that part of civil works involving the use of soil and rock
materials and the inspection or testing of the construction thereof; and an Oregon Certified
Engineering Geologist (per ORS 672.505 and 672.525), who by training, education, and
experience is especially qualified to apply geologic data, principles and interpretation to
naturally occurring materials so that geologic factors affecting planning, design, construction
and maintenance of civil engineering works are properly recognized and utilized.
Representative Disturbed Sampling: Soil samples taken at the site that have been
disturbed or altered, completely or partially, by the remolding action of sampling but which
contains all of the soil components in their in-situ (original) amounts.
Significant Structures and/or Facilities: All pavement structures for arterial and
collector streets and all building structures except one and two family dwellings, garages,
carports, and outbuildings for one and two family development.
Small Project: Examples of small projects are: (a) a utility excavation no more than
five (5) feet deep and less than 300 feet long; and (b) road reconstruction, rehabilitation,
widening, or extension of less than 300 feet of road in an area with established infrastructure
(roads, utilities). Small projects can also include sidewalk construction in an area with
established infrastructure.
Soil Description and Classification: In the Eugene/Springfield area, soil units are
Quaternary in age (younger than 1.64 My). Soil units include fluvial deposits (alluvium) and
slope deposits (colluvium). PDS (Partly Decomposed State) and CDS (Completely
Decomposed State) rock, although exhibiting characteristics of a soil, should not be
classified as a soil unit for the purpose of geological and geotechnical investigation and
design reports. Soil materials are described and classified on the basis of ASTM or
AASHTO tests for the following properties: origin: whether residual, colluvial, or
transported; gradation: measured or estimated grain size distribution; angularity/roundness
of visible soil particles; color; measured or estimated in-place moisture content; Atterberg
limits: liquid limit, plastic limit, plasticity index of the -40 fraction; relative density if non-
plastic or below the plastic limit; consistency if above the plastic limit; Expansion Index;
and, Unified Soil Classification System designation, determined by: gradation and Atterberg
limits (ASTM D-2487, UBC 18-1 or equivalent) or the Visual Manual Procedure (ASTM
D-2488 or equivalent).
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Soil Disturbance: Excavation and/or fill activities that changes the natural ground
elevation of the site by more than one (1) foot.
Undisturbed Sample: A soil sample that has relatively unaltered in-situ particle
structure and contains all of the soil components in their in-situ amounts, configuration, i.e.
initial void ratio; orientation; and degree of saturation, i.e. moisture content.
Uniform Area: An area of land:
(1) That has a single topographic feature (e.g. flat area, uniformly sloping
area) without surface indications of changes in the subsurface (soil/rock stratigraphy,
relative position of the water table);
(2) For which published information indicates that rock and soil types
over the area of the project have similar physical properties for purposes of design;
and
(3) F or which there is no significant variation in vegetation, such as, but
not limited to wet spots with sedges.
Units: Rock-, Soil-, Fill-Units. Elements in the geologic stratigraphy of the site
which affect the planning, engineering, and construction of the project. Units should be
unequivocally identifiable in the field by qualified professionals and mapable at an
appropriate scale (e.g. 1" = 1 0').
(1) A rock unit consists of a single rock type of similar origin, which
may be present in differing states of decomposition. The engineering properties of
the various states of decomposition are likely to be significantly different. In general,
a decrease of weathering and increase in strength can be expected with depth within
a single rock unit, although exceptions to this rule are frequent;
(2) A soil unit (also referred to as a "soil type") consists of soil materials
naturally present at a site, with very similar index and engineering properties; and
(3) A fill unit consists of material placed during previous construction
activities at a site. A fill unit has similar index and engineering properties.
Zone of Influence: That land area adjacent to vehicular access ways that includes
the slope easement, the soil structure beneath the road foundation slope profile extended
downhill, and the soil layer above the road slope profile extended uphill.
R-9.6710-B Purpose.
These Standards for Geological and Geotechnical Analysis describe the investigation and
report content necessary to ensure that for planning review and approval, public and private facilities
in developments in areas of known or potential unstable soil conditions are located, designed, and
constructed in a manner that provides for the public health, safety, and welfare. It is a design
professional's responsibility to ensure that the final project has sufficient geological investigation
to design and construct the proposed facilities for long-term safety, structural stability and soundness.
R-9.6710-C Applicability.
1. Except for the exemptions set forth in EC 9.6710(3), as reflected in R-9.6710-D, a
geological and geotechnical analysis prepared by an Oregon licensed Certified Engineering Geologist
or an Oregon licensed Civil Engineer with geotechnical experience is required for:
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1.1 All proposed tentative planned unit development, site review, or subdivision
applications on properties with slopes equal to or greater than 5%; and
1.2 All proposed development that includes dedication or construction of a public
street or alley or the construction of public drainage systems or public wastewater sewers.
2. All design and construction recommendations for public improvements must be
consistent with the adopted City of Eugene Public Improvement Designs Standards and APW A
Standard Specifications for Public Works Construction and Amendments.
3. As provided in EC 9.6710(5), unless exempt, the category of geological and
geotechnical analysis required is based on the following.
3.1 A Level 1 analysis shall be required on:
3.1.1 All development sites with slopes less than 10% that include
construction of public improvements;
3.1.2 Subdivision, site review, and planned unit development applications
for development sites with slopes greater than or equal to 5% and less than 10%;
3.2 A Level 2 analysis shall be required on:
3.2.1 All development sites with slopes greater than or equal to 10% that
include construction of public improvements;
3.2.2 Subdivision, site review, and planned unit development applications
for development sites with slopes greater than or equal to 10%; and
3.3 A Level 3 analysis shall be required on development sites where the Levell
or Level 2 analysis reveals evidence of existing or potential stability problems or where site
conditions such as springs or seeps, depth of soil to bedrock, variations in soil types, or a
combination of these conditions, in the opinion of the professional, impact the design
parameters of the structure.
4. Modifications to the accepted geological and geotechnical report(s) made during
construction must be reviewed and accepted by the City prior to implementation.
R-9.6710-D Exemptions.
As provided in EC 9.6710(3), the following activities are exempt from the requirements of
EC 9.6710 and the provisions of this rule:
1. Maintenance, operation, reconstruction of existing streets, driveways, and utility lines,
provided soil disturbance is limited to a standard utility trench width or the area beneath street and
driveway structures.
2. Emergency actions which must be undertaken immediately or for which there is
insufficient time for full compliance when it is necessary to prevent or abate any of the following:
2.1 An imminent threat to public health or safety;
2.2 An imminent danger to public or private property; or
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2.3 An imminent threat of serious environmental degradation.
3. Street and alley dedications that widen existing public right-of-way are exempt from
the requirements ofEC 9.6710(2)(b) and R-9.6710-C.1.2.
4. A residential building permit for a lot or parcel that was subject to previous reports
and assessments.
5. New construction, building alterations and building additions that will not result in
soil disturbance.
6. Activities on land included on the City's acknowledged Goal 5 inventory.
7. Development activities that are part of an application proposing needed housing.
R-9.6710-E Investieation and Report Content.
As provided in EC 9.671 0(4), there are three levels of detail that establish the requirements
for investigation methods and report content for a geological and geotechnical analysis (R-9.671 O-F-
G-H). Site investigations for each level largely differ in the type and complexity of the methods
used. R-9.6710-F, R-9.6710-G, and R-9.6710-H provide the acceptable methods to be used for
investigating and reporting the geological and geotechnical site investigation for Levels, 1, 2, and
3 respectively. These requirements are designed to ensure objective means for:
1.1 Validity and reproducibility of the results;
1.2 Evaluation of adequacy of the geological and geotechnical investigation and
design recommendations;
1.3 Evaluation of proposed engineering and construction methods during the
design phase; and
1.4 Confirmation of the findings by qualified City inspectors during
implementation of the project.
A report of the required level of investigation must be made and three (3) copies submitted
with the land use development application and/or construction permit application.
R-9.6710-F Levell - Investieation Methods and Report Content.
1. Site Characteristic Investieation. A Level 1 investigation shall consist of:
1.1 A compilation of record geotechnical data, on-site verification of the data and
site conditions and a discussion of the methodologies used;
1.2 A report discussing site and soil/rock characteristics in relation to the
proposed development and including any office or field evidence of expansive soils or
flooding.
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A Levell investigation does not require any digging or drilling at the project site. A Level
1 investigation must include an examination of existing exposures such as, but not limited to, road
cuts.
2. Investieation Methods.
2.1 Literature Survey and Observations. An estimate of the soil/rock profile shall
be made, based on the following geological and pedological literature and maps (required
sources are in bold) information, when available:
2.1.1 USGS 7.5' Quadrangle Topographic Map.
2.1.2 USDA Soil Survey of Lane County Area, Oregon (website:
http://ice.or.nrcs.usda.gov/website/soils/oregonlor _reports _ or.htm).
2.1.3 Historical aerial photos (U of 0 MAP Library).
2.1.4 USGS OM-I10 (Geology of the Southern and Southwestern Border
Areas of the Willamette Valley, Oregon, 1951).
2.1.5 USGS Water Resources Paper 2018 (Groundwater Resources of the
Eugene/Springfield Area, 1973).
2.1.6 USGS 1 :250,000 Geologic Map of the Salem Quadrangle.
2.1.7 Geologic Map of Oregon (USGS, 1991).
2.1.8 Relative Earthquake Hazard Map of the Eugene-Springfield
Metropolitan Area, Lane County, Oregon, IMS-14 Oregon Department of Geology
and Mineral Industries (DOGAMI), 2000.
2.1.9 Records of former City of Eugene, state, and federal public works
projects at or near the proposed development site.
2.1.10 Other sources of information about the site, including geology-based
theses and dissertations prepared by students at University of Oregon or Oregon State
University, studies made by local and regional planning boards, and knowledgeable
individuals such as university professors, reference librarians, geotechnical
engineering firms, engineering geology firms, site exploration firms, local quarry
operators, construction aggregate suppliers, and appropriate persons from agencies
such as State geological surveys, the US Geological Survey (USGS), and the US
Army Corps of Engineers (ACOE).
2.2 Site Investigation. The site visit shall focus on conditions, such as, but not
limited to, the presence of expansive soil, potential and/or existing instability, shallow
groundwater or surface water, presence of fill, and hazardous materials. The site
reconnaissance shall be performed by a Qualified Registered Professional and include the
following items (as applicable):
2.2.1 Verify topography as indicated on contour map. Measure maximum
slopes using clinometer or equivalent.
2.2.2 Check existing cuts/exposures to determine soil depth, characteristics,
classification and/or rock type/weathering state/depth.
2.2.3 Check for evidence of seeps/springs and vegetation characteristics
2.2.4 Check for evidence of slope movement/creep, including leaning
conifers, pistol-butts on trees, sweeps (long curved sections)on conifers, and
topographic features.
2.2.5 Check performance of any structures, including structures on
adjoining properties, by noting any cracking/uneven pavement, cracked/separated
sidewalks and driveways, uneven roof-lines and/or cracked/separated foundations.
2.2.6 If possible, contact owners/contractors of adjacent lots to evaluate
anecdotal observations of the site and surrounding area in regard to soils, hydrology,
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and construction difficulties.
2.2.7 Measure slopes in the project area.
3. Report Content.
3.1 Introduction:
3.1.1 Purpose and scope of investigation.
3.1.2 Client or party that commissioned the report.
3.1.3 Authorization for study.
3.2 Prol ect Location and Description:
3.2.1 Site location and description, including topography, slopes within and
adjacent to the project.
3.2.2 Description of proposed development, structures, and/or facilities.
3.2.3 Description of previous investigations, existing or previous structures
on the site, project file data, and anecdotal information from residents, as applicable.
3.2.4 Geologic setting -- discussion, based on literature survey, of the local
surficial geology that may affect the project and potential geologic-natural hazards,
including potential seismic hazard.
3.2.5 Site reconnaissance observations -- topography; slopes; exposures;
condition of on-site and adjacent structures; drainage features, vegetation.
3.3 Conclusions.
3.3.1 Summary of site subsurface soil/rock conditions, based on literature
survey and site reconnaissance.
3.3.2 Indications of the absence or presence of potentially expansive soils,
organic deposits, loose sands, and other unstable soils at critical locations with
respect to the structure or facility.
3.3.3 Recommendation for acceptance of site without further investigation
or recommendations for making a higher level of investigation, with reasoning for
the recommendation.
3.4 Appendices.
3.4.1 Site location map.
3.4.2 Map showing areas of potential geologic-natural and/or seismic
hazards, if any (by inclusion or by reference).
3.4.3 Map showing contours, drainage features, seeps, springs, wetlands,
open waterways.
3.4.4 Grading Plan.
3.4.5 Footnote or bibliography references to pre-existing information,
including published literature, geologic maps, and other applicable resources.
4. Review and Determination. Further geological and geotechnical investigation is
required when one of the following circumstances exist:
4.1 The analysis reveals evidence of existing or potential stability problems;
4.2 In the Qualified Registered Professional's opinion, site conditions such as
springs, seeps, depth of soil to bedrock, variations in soil types, or a combination of these
conditions will impact the design parameters of the structure.
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If either of the circumstances listed in 4.1 or 4.2 exist, a Level 3 analysis must be submitted.
R-9.6710-G Level 2 - Investi~ation Methods and Report Content.
1. Geolo~ic Investi~ation. A Level 2 investigation shall consist of:
1.1 A Level 1 investigation;
1.2 Subsurface investigation and testing to establish soil types and distribution,
based on representative disturbed sampling of soil and/or rock using dug pits or trenches,
hand augers, bucket augers, borings or other exploratory methods. The investigation shall
be designed to provide the following information (as applicable for the proposed
development):
1.2.1 Lateral/vertical distribution of soil and/or rock unites); and,
1.2.2 Classification and index properties of the soil and rock unites); and,
1.2.3 Location of static water level or piezometric surface (including
seasonal variation).
The subsurface investigation shall delineate design area( s) and determine the index properties
of the soil/rock to a sufficient depth below the structure or facility (see Exhibit A); and
1.3 A report that includes site and soil characteristics in relation to the proposed
development, identification of potential problems, and recommendations for design and
construction techniques and standards consistent with other standards applicable to the
development proposal. The investigation report shall classify all soil types encountered
using the Unified Soil Classification System (Exhibit B), AASHTO classification (Exhibit
C), or the Uniform Building Code Standard 18-1 (Exhibit D), and all rock types using an
engineering rock classification system. Classification shall be done by visual-manual
methods and confirmed by laboratory index properties tests of typical samples. Engineering
properties tests, field or laboratory, are not required. Water levels shall be observed in pit
excavations or borings.
2. Investi~ation Method.
2.1 Methods for Making Pits. Trenches. and/or Borings. Excavations for
sampling of soils/rock from below the surface may consist of pits, trenches, or borings, made
by hand or by machine. Any device, such as a backhoe, excavator, hand auger, machine
auger, thick wall tube, or vibrating tube that will permit excavation to the desired sampling
depth and allow access for representative disturbed sampling of the soil or rock is acceptable.
2.2 Number and Locations of Pits and/or Borings. The spacing, locations and
depths of pits, trenches, or borings shall be in accordance with the provisions of Exhibit A,
"Minimum Requirements for Spacing and Depth of Pits and Borings for Sampling Soils and
Rock. "
2.3 Index Properties of Soil or Rock. Significant index properties of soil include
texture (grain size distribution), Atterberg limits, Plasticity Index, Expansive Index, void
ratio, organic content, and relative density and/or consistency. Significant index properties
of rock include color, texture, degree of weathering, hardness, and geologic name. Index
properties are to be identified, by laboratory tests or by visual-manual method, and described
for each soil unit found in the subsurface investigation.
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3. Report Content.
3.1 Introduction. Must include the same information required in a Levell report.
3.2 Prol ect Location and Description. Must include the same information required
in a Level 1 report.
3.3 Site Investigation.
3.3.1 Development of the investigation. (Include who specified it and why
the investigation was done in the manner it was done.)
3.3.2 Scope of field work. (Include how many test pits/test borings were
made, what type, and where.)
3.3.3 Drilling, sampling, and field testing program and methods;
ASTM/ AASHTO references.
3.3.4 Laboratory testing program (samples tested; procedures used, ASTM
references).
3.3.5 Discussion ofunusual conditions encountered during field drilling and
sampling.
3.4 Analysis of Site Investigation Data.
3.4.1 Summary of observed subsurface profile (stratigraphy); discussion of
soil and rock layers and deposits encountered in the subsurface investigation; index
properties and classifications.
3.4.2 Comparison of developed soil profile to geologic setting described in
previous section, including a discussion of similarities and differences.
3.4.3 Discussion of each of the potential geologic-natural hazards observed
at the development site; location, magnitude, time effects, possible effects on the
structure or facility.
3.4.4 Discussion of laboratory test results, and description of potentially
expansive soils, organic deposits, loose sands, and any areas of potential or existing
instability.
3.4.5 Discussion of anticipated groundwater conditions that may effect the
site development and/or project, and discussion of effects of grading on infiltration
of water.
3.5
following:
Conclusions. Include the same requirements required in a Level 1 and the
3.5.1 Suggested methods for dealing with the potential geologic-natural
hazards; qualitative advice to design engineers or architects.
3.5.2 Clear reference to empirical, published or unpublished, minimum
design standards or procedures for the design of elements of the structure or facility,
which are based solely on the index properties of supporting soil and/or rock units.
Recommendations for design and construction shall be based on the Qualified
Registered Professional's judgment, combined with experience.
3.5.3 Expectations concerning consolidation or settlement.
3.5.4 Clear reference of groundwater elevations and its impact on the
constructed development and construction activities and necessary mitigation
measures.
3.6 Appendices and Graphic Presentations. Shall meet the same requirements
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required in a Level I and include the following:
3.6.1 Plot plan showing locations of borings and test pits.
3.6.2 Logs of borings and/or observations pits, including all sampling data
and water level measurements.
3.6.3 Soil profile drawing showing estimated stratigraphy and the locations
of field samples and observed water levels.
3.6.4 Map showing boundaries of units.
3.6.5 Map showing areas of potential geologic-natural and/or seismic
hazards, if any (by inclusion or by reference in body of text).
3.6.6 Map defining and delineating the sequence, distribution, and
characteristics of soil/rock materials throughout the site.
4. Review and Determination. Further geological and geotechnical investigation is
required when one of the following circumstances exist:
4.1 The analysis reveals evidence of existing or potential stability problems;
4.2 In the Qualified Registered Professional's opinion, site conditions such as
spring, seeps, depth of soil to bedrock, variations in soil types, or a combination of these
conditions will impact the design parameters of the structure.
If either of the circumstances listed in 4.1 or 4.2 exist, a Level 3 analysis must be submitted.
R-9.6710-H Level 3 - Investi~ation Methods and Report Requirements.
1. Geoloeic Investi~ation with Geotechnical Desi~n Details. A Level 3 investigation
shall consist of:
1.1 The information required for a Level 1 and Level 2 investigation;
1.2 Site-specific geotechnical design of facilities such as, but not limited to,
streets, foundations, utilities, retaining walls and structures due to topographic and geologic
constraints;
1.3 Resul ts 0 f test borings and/or test pits and field strength tests such as Standard
Penetration Test (SPT) or other field tests that measure the strength and competency of the
soils. Field measurements of aquifer characteristics using pumping tests or slug tests are
acceptable. Undisturbed samples of cohesive soils may be taken for laboratory tests such as
unconfined compression, triaxial compression, direct shear, consolidation, and/or
permeability.
2. Investi~ation Methods.
2.1 Methods for Making Test Borings or Test Pits. Excavations for undisturbed
sampling and/or field testing of soils/rock must consist of borings or pits, made by hand or
by machine. Any device, such as a backhoe, excavator, auger boring, wash boring, or mud-
rotary boring that will permit excavation to the desired sampling or testing depth and will
permit undisturbed sampling using thin-wall tubing or core barrel, as appropriate, and/or
field testing of the soil or rock is acceptable.
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2.2 Number and Locations of Test Borings or Test Pits. The spacing, locations
and depths of pits, trenches, or borings shall be in accordance with the professional judgment
of the Qualified Registered Professional of record.
2.3 Engineering Properties of Soil. The engineering, or physical, properties of
soil and rock depend on both the material, or grain, properties (see Level 2 above) and the
in-situ, or undisturbed, texture, packing, particle orientation, and degree of saturation. Shear
strength, compressibility, permeability, and erodibility are the engineering properties of
interest. Tests for estimating the in-situ shear strength and compressibility of a soil include:
(1) direct tests, that attempt to measure the shear strength by direct simulation of field
loading conditions and (2) indirect tests that are used with empirical correlations to estimate
shear strength in terms of relative consistency (cohesive soils) and relative density (granular
soils). Field tests for measuring the permeability of an aquifer may be made using pumping
out tests or slug tests. Anyone, or a combination, of the following tests or procedures may
be made to determine or estimate shear strength properties of the various soil types and
deposits encountered in the test borings or test pits.
2.3.1 Direct measures of in-situ shear strength include:
2.3.1.1 Plate Load Test (ASTM DI194).
2.3.1.2 Field Vane Shear Test (VST) of Cohesive Soil (ASTM
D2573).
2.3.1.3 Borehole Shear Test (BST).
2.3.1.4 Unconfined Compression Test of Undisturbed Cohesive
Sample (ASTM D2166).
2.3.1.5 Hand Penetrometer Test of Cohesive Sample (Used only for
secondary evaluation).
2.3.2 Indirect, empirical estimators of in-situ shear strength are:
2.3.2.1 Standard Penetration Test (SPT) (ASTM D 1586).
2.3.2.2 Static Cone Penetration Test (CPT) (ASTM D 3441).
2.4 In-Situ Character of Rock. The engineering characteristics of an in-situ rock
mass generally are concerned with its structural elements. Discontinuities are the major
elements of in-situ classification. Fractures in exposed rock surfaces are described in terms
of frequency, attitude, spacing, roughness, bonding quality, and general continuity. The main
tests made on rock cores, taken with a diamond core barrel sampler, are:
2.4.1 Unconfined compressive strength and/or point load strength.
2.4.2 Rock Quality Designation (RQD).
2.4.3 Seismic velocity and/or velocity index.
3. Report Content.
3.1 Introduction. Must include the same information required in a Levell report.
3.2 Prolect Location and Description. Must include the same information
required in a Levell report.
3.3
report.
Site Investigation. Must include the same information required in a Level 2
3.4 Analysis of Site Investigation Data. Must include the same information
required in a Level 2 report, including results of laboratory tests.
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3.5 Geotechnical Engineering Design Recommendations Specific to the Prolect.
3.5.1 Summary and design requirements for significant structures and/or
facilities. Analyses and studies, including alternatives.
3.5.2 Shallow and/or deep foundation design recommendations.
3.5.3 Discussion of potential seismicity and potential geologic hazards at
the site and proposed designs to mitigate effects.
3.5.4 Seismic site hazard report, if required by the state building code,
including recommendations for foundation criteria.
3.5.5 Landslide mitigation and/or repair recommendations.
3.5.6 Suitability of on-site and imported soils for use in compacted fill.
3.5.7 Treatment of cut/fill lines or other differential transition beneath
improvements.
3.5.8 Retaining structure design recommendations.
3.5.9 Earthwork structures design recommendations.
3.5.10 Compacted fill materials and construction methods recommendations.
3.5.11 Street, roadway, or airfield pavement soils-related design
recommendations.
3.5.12 Access construction across slope easements.
3.5.13 Zone of influence setbacks and construction constraints.
3.5.14 Summary of geologic risks, constraints such as expansive soil which
cannot be mitigated by removal, and/or potential or existing landslide areas and
mitigation measures.
3.6 Construction Considerations.
3.6.1 Recommended construction procedures and considerations for
drainage, backfill materials, compaction requirements, weather limitations, quality
assurance program.
3.6.2 Inspection requirements during and following construction.
3.7 Appendices. Tables. and Graphic Presentations. Shall meet the same
requirements required in Levels 1 and 2, and include the following:
3.7.1 Tabulated summary of laboratory test results (if not included in body
of report).
3.7.2 Calculations and recommended design details for shallow and/or deep
foundation elements.
3.7.3 Calculations and recommended design details for retaining structures
and/or excavation bracing.
3.7.4 Recommended specifications for general earthwork fill and for
landslide repairs, including acceptable soil or rock types, fill placement methods and
requirements and quality assurance procedures.
3.7.5 Slope stability studies; recommended design details for cut slopes
and/or reinforced slopes.
3.7.6 Site drainage studies; recommended design details for drainage
methods and structures.
3.7.7 Special calculation sheets for unusual structures and recommended
design details.
3.7.8 Alternative analyses and studies.
4. Review and Determination. The City shall not accept or approve a Level 3 analysis
unless the following conditions have been met or satisfied:
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4.1 The investigation has incorporated all geological and geotechnical
requirements for the design and construction of the proposed facility and/or structures;
4.2 The preliminary slope easements and zones of influence are determined;
4.3 The geotechnical requirements for vehicular access to the site are identified
in the report;
4.4 Roadside retaining walls are designed in accordance with Oregon Department
of Transportation's retaining wall manual or other authoritative source;
4.5 The restricted zone above foundation and retaining walls where structural
loads should not be placed are included in the report;
4.6 Additional work necessary prior to approving final development applications
is identified in the report;
4.7 Potential geological site constraints and hazards have been identified and
mitigated; and
4.8 Any findings and design mitigation measures have been reviewed and
accepted by the City Engineer.
R-9.671 0-1 Seal and Sienature Required.
All reports shall be signed and sealed by either an Oregon Registered Professional Engineer
or an Oregon Certified Engineering Geologist. Assignment of work and authority to sign and seal
reports is dictated by Oregon Revised Statutes Chapter 672.
R-9.6710-J Alternative Methods of Investi~ation.
1. These standards are not intended to unreasonably limit any innovative or creative
investigative methods that could result in better quality and/or lower costs. A determination to allow
a proposed departure from the required standards for methods of investigation shall be based on
findings by the City that the proposal will produce a compensating or comparable result to the
required standard(s), that is in every way adequate for the user and the City.
2. A non-standard method of investigation and corresponding analysis may take longer
to review, resulting in increased processing costs being incurred by the applicant. This information
shall be conveyed to an applicant, who, by filing an application for a non-standard analysis for
review, acknowledges and agrees to pay the potentially increased processing costs. An applicant
seeking approval of an alternate method of investigation also acknowledges that it remains the
Qualified Registered Professional's responsibility to ensure that the final project has sufficient
geological investigation so that the proposed facilities can be designed and constructed in a manner
that provides long-term safety, structural stability and soundness.
3. Requests for deviations from the investigation methods required by these standards
shall be provided in writing and reviewed by the City. The City's decision to grant, deny, or modify
the proposed deviation shall be made within 30 days of receipt of the written request and will be
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based upon evidence that the deviation request meets all of the following criteria:
3.1 The alternate investigation method will have sufficient geological
investigation to locate, design and construct the proposed facilities for long-term safety,
structural stability and soundness through a comparable or superior design;
3.2 The alternative will not adversely affect health, public safety and welfare,
and/or operation of the structure(s); and
3.3 The alternative will not adversely affect maintainability of the structure(s).
This Rule shall become effective 30 days from the date that it is adopted as indicated below.
This Rule shall apply only to land use applications submitted after the Rule's effective date.
Dated 31 day of M /.}ReI-( , 2003.
~~ f2 ~(r
'. James R. Carlson
!--- City Manager pro tern
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EXHIBIT A
MINIMUM REQUIREMENTS FOR NUMBER AND SPACING
OF PITS AND BORINGS FOR SAMPLING SOilS AND ROCK
Number and spacing of Level 2 sampling pits or borings and Level 3 test borings should conform to the following
guidelines. For Level 3, the Geotechnical Engineer will select the locations of borings and the type, freq uency, and depth
of samples and/or field strength tests.
Guidelines for Spacing of Borings I
Maximum distance between borings, feet
Project Horizontal stratification of soil or rock Minimum number of borings
Uniform Average Non-uniform
Multi-story buildings 150 100 50 4 per structure
One or two-story buildings 200 100 50 3 per 1 structure
Land divisions, development site 500 200 100 2 per acre
4 or less acres
Land divisions, development site 500 200 100 Minimum 8 per site with 3
4 or more acres per soil unit
Bridge piers, abutments, 100 100 25
television towers, etc.
Roadways, sewers, pipelines 1000 500 200 - 100
Borrow pits 500 200 100 - 50
(for compacted fill)
Earth dams, dikes 200 100 50
Space preliminary borings 200 to 500 feet apart so that the area between any four
New site of wide extent borings includes approximately 10% of the total area. In detailed exploration, add
borings to establish geological sections at the most useful orientation.
Development of site on soft Space borings 100 to 200 feet at possible building locations. Add intermediate
compressible strata borings when building site is determined.
Low-load warehouse building or Minimum of 4 borings at comers plus intermediate borings at interior foundations
large area sufficient to define subsoil profile.
Slope stability, deep cuts, high Provide 3 to 5 borings on line in the critical direction to provide geological section
for analysis. Number of geological sections depends on extent of stability
embankments problem. For active slide, place at least one boring up slope of sliding area.
Page 1 of2
Guidelines for Depth of Borings
Area for
Investigation
Structural Foundation
~arge Structure with
~eparate closely spaced
ootings.
solated rigid foundation.
~ighways and airfields;
pipe lines.
Retaining walls.
Slope stability.
Cuts.
Embankments.
Boring Depth
The depth of borings depends upon the soil profile and the type of feasible foundation.
Proceed as follows: (1) If no preliminary soil information is available, start with one or two
deep borings to bedrock or to a depth equal to the width of the structure. (2) Analyze the
boring results and determine the number and depths of additional borings.
Borings should be carried to a depth:
1. below any organic soils, muck, artificial fill, or compressible layer;
2. sufficiently deep for establishing the bottom elevation of foundation (footings, piles, or
caissons); and
3. sufficiently deep for checking the possibility of a weaker soil, at a greater depth, which
may settle under the sustained load.
Extend to a depth where increase in vertical stress for combined foundations is less than
10% of effective overburden stress. Generally all borings should extend to no less than 30
feet below lowest part of the foundation unless rock is encountered at shallower depth.
Extend to a depth where increase in vertical stress decreases to 10% of bearing pressure.
Generally all borings should extend to no less than 30 feet below lowest part of the
foundation unless rock is encountered at shallower depth.
Minimum depth of borings is 5 ft below bottom of structure, but should extend below
organic soil, muck, artificial fill, or compressible layers such as soft clays and silts.
1. Below organic soil, muck, artificial fill, or compressible layer;
2. deeper than poSSible surface of sliding; and
3. deeper than width of the base of wall.
Extend to an elevation below active or potential failure surface and into hard stratum, or tc
a depth for which failure is likely because of geometry of cross section.
Extend to:
1. below organic soil, muck, artificial fill, or compressible layer;
2. deeper than possible surface of sliding; and
3. depth between % to 1 times base width of narrow cuts.
Where cut is above ground water in stable materials, depth of 4 to 8 feet below base may
suffice. Where base is below groundwater, determine extent of pervious strata below
base.
Extend to:
1. below organic soil, muck, artificial fill, or compressible layer,
2. deeper than possible surface of sliding; and
3. depth between % to 1 ~ times horizontal length of side slope in relatively homogeneous
foundation.
Where soft strata encountered, borings should reach hard materials.
Page 20f2
EXHIBIT B
UNIFIED SOIL
CLASSIFICATION SYSTEM
UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART
COARSE-GRAINED SOILS
(more than 50% of material Is larger than No. 200 sieve size.)
Clean Gravels Less than 5% fines
.~::~ Well-graded gravels, gravel-sand
.:.. mixtures, little or no fines
FINE-GRAINED SOILS
(50% or more of material is smaller than No. 200 sieve size.)
Inorganic silts and very fine sands, rock
flour, silty of clayey fine sands or clayey
silts with slight plasticity
Inorganic clays of low to medium
plasticity, gravelly clays, sandy clays,
silty clays, lean clays
GRAVELS
More than 50%
of coarse
fraction larger
than NO.4
sieve size
SANDS
50% or more
of coarse
fraction smaller
than NO.4
sieve size
SILTS
AND
CLAYS
Liquid limit
less than
50%
SILTS
AND
CLAYS
Liquid limit
50%
or greater
HIGHLY
ORGANIC
SOILS
PoorIy-graded gravels, gravel-sand
mixtures, little or no fines
Gravels with fines More than 12% fines
Silty gravels, gravel-sand-silt mixtures
~~~ SC
Clayey sands, sand-clay mixtures
ML
CL
OL
Organic silts and organic silty clays of
low plasticity
MH
Inorganic silts, micaceous or
diatomaceous fine sandy or silty soils,
elastic silts
CH
Inorganic clays of high plasticity, fat
clays
OH
Organic clays of medium to high
plasticity, organic silts
PT
Peat and other highly organic soils
lABORATQRY CLASSIFICATION CRITERIA
CU Oso 030
GW = - greater than 4; Cc = - between 1 and 3
010 010 xOso
GP Not meeting all gradation requirements for GW
GM Atterberg limits below wAw Above W A W line with P.1. between
line or P.l.less than 4
4 and 7 are borderline cases
GC Atterberg limits above wN requiring use of dual symbols
line with P.1. greater than 7
Oso 030
SW Cu = - greater than 4; Cc = - between 1 and 3
010 010 xOso
SP Not meeting all gradation requirements for GW
SM Atterberg limits below wAw Limits plotting in shaded zone
line or P.1. less than 4 with P.1. between 4 and 7 are
Atterberg limits above wAw borderline cases requiring use
SC line with P.1. greater than 7 of dual symbols.
Determine percentages of sand and gravel from grain-size curve. Depending
on percentage of fines (fraction smaller than No. 200 sieve size).
coarse-grained soils are classified as follows:
Less than 5 percent . . . . . . . . . . . . . . . . . . . . . . . . . . . .. GW, GP. SW. SP
More than 12 percent .. . . . . . . . . . . . . . . . . . . . . . . ... GM. GC, SM. SC
5 to 12 percent . . . . . . . . . . . . . .. Borderline cases requiring dual symbols
PLASTICITY CHART
60
~ 50
~
>< 40
w
0
~ 30
~
(3 20
i=
rn
j 10
tl.
/
CH / /'
~ A LINE:
PI = 0:73Cll..-2O)
../ I
CL MH&OH
;/
/
......... . ML&PL
.... = ~
00 10 20 30 40 50 60 70 80 90 100
LIQUID LIMIT (lL) (Of.)
EXHIBIT C
General Granular materials Sill-clay materials
c1assification (35 percent or less of total sample passing No. 200) (More than 35 percent of total
sample passing No. 200)
I
Group A-' A-3 A-2 A-4 A-5 A-6 A-7
classification A-7 -5"
A-'- a A-'-b A-2-4 A-2-5 A-2-6 A~2-7 A-7 -6
Sieve analysis
percent passing
No. 10 50 max
No. 40 30 max 50 max 5' min
No. 200 15 max 25 max 10 max 35 max 35 max 35 max 35 max 36 min 36 min 36 min 36 min
Characteristics of
fraction passing
No. 40
Liquid limit. IC/. 40 max 41 min 40 max 41 min 40 max 41 min 40 rnax 41 min
Plastic Index. 1/. 6 max NP 10 max 10 max 11 min 11 min 10 max 10 max 11 min 11 min
Significant constituent gravel and fine silty and clayey silty soils clayey soils
materials sand sand gravel and sand
nSee Fig. 8-1b
(a) AASHTO Soil Classification System soil groups. A-8 (not shown) is peat or muck classified visually.
70
10
I I I I I I 7
Note: A-2 soils contain I~ss than
I---~ 35% finer than No. 200 sieve. V
V
V
V
/~y
:7
A-7 -6 ~
\1
V
/
A-6 and A-2-6 7
7 A-7.5 and A-2-7
/
A-4 and A-2-4 A-51 and '"}-2-5
I I
60
50
-"-
x 40
Q)
"0
c:
~
'u
~= 30
(1)
a::
20
o
o
10
20
30
40
50
Liquid limit W L
60
70
80
90
100
(b) Liquid-limit and plasticity index ranges for group classification of silt-clay materials. (Standard SpecificatiO'Tl.$ for 7rans-
portation Mat.e'lials and Methods of Sampling and 'Iesting, 15th ed., Washington, DC., American Association of State
Highway and 'Ihnsportation Officials, Copyright 1990. Us~ by permission.)
Figure 8-1
Charts for use in AASHTO Soil Classification System.
80
8: Classification of Soils
J 1
EXHIBIT D
.."..,. """'.... ---. .... --.---..- ----
"" ."'....,"".,""' .u-.
UNIFORM BUILDING CODE STANDARD 18-1
SOILS CLASSIFICATION
Based on Standard Method D 2487-69 of the American Society for Testing and Materials.
Extracted, with permission, from the Annual Book of ASTM Standards, copyright American Society for
Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428
See Sections 1801.2 and 1803.1, Unfform Building Code
SECTION 18.101 - SCOPE
This standard describes a system for classifying mineral and or-
ganomineral soils for engineering purposes based on laboratory
determination of particle-size characteristics, liquid limit and
plasticity index.
SECTION 18.102 - APPARATUS
Apparatus of an approved type shall be used to perform the fol-
lowing. tests and procedures: Preparation of soil samples, liquid
limit test, plastic limit test and particle-size analysis.
SECTION 18.103- SAMPUNG
Sampling shall be conducted in accordance with approved meth-
ods for soil investigation and sampling by auger borings, for Pene-
tration Test and Split-barrel Sampling of Soils, and for
Thin-walled Thbe Sampling of Soils.
The sample shall be carefully identified as to origin by a boring
number and sample number in conjunction with a job number, a
geologic stratum, a pedologic horizon or a iocation description
with respect to a permanent monument, a grid system or a station
number and offset with respect to a stated center line.
The sample should also be described in accordance.with an ap-
proved visual-manual procedure. (A soil which is composed pri-
marily of undecayed or partially decayed organic matter and has a
fibrous texture, dark brown to black color, and organic odor
should be designated as a highly organic soil,. PT, and not sub-
jected to the classification procedures described hereafter.)
SECTION 18.104 - TEST SAMPLE
Test samples shall represent that portion of the field sample finer
than the 3-inch (76 mm) sieve and shall be obtained as follows:
Air dry the field sample; weigh the field sample; and separate
the field sample into two fractions on a 3-inch (76 mm) ~ieve.
Weigh the fraction retained on the 3-inch (76 mm) sieve. Compute
the percentage of plus 3-inch (76 rom) material in the field sample
and note this percentage as auxiliary information. Thoroughly
mbnhe fraction passing the 3-inch (76 mm) sieve and select test
samples.
SECTION 18.105 - PREUMINARY CLASSIFICATION
PROCEDURE
Procedure for the determination of percentage finer than the No.
200 (75 J.lm) sieve is as follows:
1. From the material passing the 3-inch (76 mm) sieve, select a
test sample and determine the percentage of the test sample finer
than the No. 200 (75 J.lm) sieve. (This step may be omitted if the
soil can obviously be classified as fine-grained by visual inspec-
tion.) .
2. Classify the soil as coarse-grained if more than 50 percent of
the test sample is retained on the No. 200 (75 JAm) sieve.
3. Classify the soil as fine-grained if 50 percent or more of the
test sample passes the No. 200 (75 J.lIl1) sieve.
SECTION 18.106 - PROCEDURE FOR
CLASSIFICATION OF COARSE-GRAINED SOILS
(MORE THAN 50 PERCENT RETAINED)
Select test samples from the material passing the 3-inch (76 mm)
sieve for the determination of particle-size characteristics, liquid
limit and plasticity index. Determine the cumulative particle-size
distribution of the fraction coarser than the No. 200 (75 J.lm) sieve.
Classify the sample as grave~ G, if 50 percent or more of the
coarse fraction [plus No. 200 (75 J.lm) sieve] is retained on the No.
4 (4.75 mm) sieve. Classify the sample as sand, S, if more than 50
percent of the coarse fraction [plus No. 200 (75 J.lm) sieve] passes
the No.4 (75 mm) sieve.
If less than 5 percent of the test sample passed the No. 200 (75
J.lIl1) sieve, compute the coefficient of uniformity, Cu, and coeffi-
cient of curvature, Cx, as given in Formulas 18-1-1 and 18-1-2:
C - D6{)' (18-1-1)
., - DIO
(D30F
CZ = D10 X D60 (18-1-2)
in which DlO, D30 and D60 are the particle size diameters corre-
sponding respectively to 10,30 and 60 percent passing on the cu-
mulative particle size distribution curve.
ClaSsify the sample as well-graded gravel, GW, or well.;graded
sand, SW, if Crt is greater than 4 for gravel and 6 for sand, and Cz is
between 1 and 3. Classify the sample as poorly graded gravel, GP,
or poorly graded sand, SP, if either the Cu or the Cz criteria for
well-graded soils are not satisfied.
If more than 12 percent of the test sample passed the No. 200 (75
J..t.ID.) sieve, determine the liquid limit and the plasticity index of a
portion of the test sample passing the No. 40 (425 J.l1ll) sieve in ac-
cordance with approved methods.
Classify the sample as silty gravel, GM, or silty sand, SM, if the
results of the limits tests show that the fines are silty, that is, the
plot of the liquid limit verSus plasticity index faUs belo~ the "A"
line (see Plasticity Table 18-1-A) or the plasticity index is less
than 4.
Classify the sampk as clayey gravel, GC, or clayey sand, SC, if
the fines are clayey, that is, the plot of liquid limit versus plasticity
index falls above the "A" line and the plasticity index is greater
than 7.
If the fines are intermediate between silt and clay, that is, the
plot of liquid limit Versus plasticity index falls on or practically on
the "A" line or falls above the "An line but the plasticity index is in
the range of 4 to 7, the soil should be given a borderline classifica-
tion, such as GM-GC or SM-SC.
If 5 to 12 percent of the test sample passed the No. 200 (75 J.tm)
sieve, the soil should be given a borderline classification based on
both its gradation and limit test characteristics, such as GW-GC or
SP-SM. (In doubtful cases the rule is to favor the less plastic clas-
3-327
STANDARD 18-1
sification. Example: A gravel with 10 percent fines, a Cu of 20, a
Cz of 2.0, and a plasticity index of 6 would be classified as
GW-GM rather than GW-Gc.)
SECTION 18.107 - PROCEDURE FOR
CLASSIFICATION OF FINE-GRAlNED SOilS
(50 PERCENT OR MORE PASSING)
From the material passing the 3-inch (76 mm) sieve, select a test
sample for the determination of the liquid limit and plasticity in-
dex. The method for wet preparation shall be used for soils con-
taining organic matter or irreversible mineral colloids.
Determine the liquid limit and the plasticity index of a portion
of the test sample passing the No. 40 (425 f.lm) sieve.
Classify the soil as inorganic clay, C, if the plot of liquid limit
versus plasticity index falls above the " A" line and the plasticity
index is greater than 7.
Oassify the soil as inorganic clay of low to medium plasticity,
CL, if the liquid limit is less than 50 and the plot of liquid limit ver-
sus plasticity index falls above the" A" line and the plasticity in-
dex is greater than 7. See area identified as CL on the Plasticity
Chart of Table 18-1-A
Oassify the soil as inorganic clay of high plasticity, CH, if the
liquid limit is greater than 50 and the plot of liquid limit versus
plasticity index falls above the "A" line. In cases where the liquid
limit exceeds 100 or the plasticity index exceeds 60, the plasticity
chart may be expanded by maintaining the same scales on both
axes and extending the c'A" line at the indicated slope. See areas
identified as CH on the Plasticity Chart, Table 18-I-A.
Oassify the soil as inorganic silt, M, if the plot of liquid limit
versus plasticity index falls below the" A " line or if the plasticity
index is less than 4, unless it is suspected that organic matter is
1997 UNIFORM BUILDING CODE
present in sufficient amounts to influence the soil properties, then
tentatively classify the soil as organic silt or clay, O.
If the soil has a dark color and an organic odor when moist and
warm, a second liquid limit test should be performed on a test sam-
ple which has been oven dried at 1l0oC :t 50C for 24 hours.
Oassify the soil as organic silt or clay, 0, if the liquid limit after
oven drying is less than three fourths of the liquid limit of the origi-
nal sample determined before drying.
Classify the soil as inorganic silt of low plasticity, ML, or as or-
ganic silt of low plasticity, ML, or as organic silt or silt-clay of low
plasticity, OJ..., if the liquid limit is less than 50 and the plot of liq-
uid limit versus plasticity index faUs below the "An line or the
plasticity index is less than 4. See area identified as ML and OL on
the Plasticity Chart, Table I8-I-A.
Classify the soil as inorganic silt of medium to high plasticity,
MH, or as organic clay or silt-clay of medium to high plasticity,
OR, if the liquid limit is more than 50 and the plot of liquid limit
. versus plasticity index falls below the "An line. See atea identified
as MH and OH on the Plasticity Chart of Table 18-I-A.
In order to indicate their borderline characteristics, some
fine-grained soils should be classified by dual symbols.
If the plot of liquid limit versus plasticity index falls on or prac-
tically on the "A" line or above the" A" line where the plasticity
index is in the range of 4 to 7, the soil should be given an appropri-
ate borderline classification such as CL-ML or CH-OH.
If the plot of liquid limit versus plasticity index falls on or prac-
tically on the line liquid limit = 50, the soil should be given an ap-
propriate borderline classification such as CL-CH or ML-MH. (In
doubtful cases the rule for classification is to favor the more. phis-
tic classification. Example: a fine-grained soil with a liquid limit
of 50 and a plasticity index of 22 would be classified as CH-MH
rather than CL-ML.)
~~)
t
:.i
/
TABLE 18-1-A-SOIL CLASSIACATION CHART
1 Based on the material passing the 3-inch (76 mm) sieve.
3-328
GROUP
.MAJOR DIVISIONS SYMBOLS TYPICAL NAMES
ClEAN GW Well-graded gravels and gravel-sand mixtures, little or no fines
GRAVELS GRAVELS GP Poorly graded gravels and gravel-sand mixtures. little or no fines
50% or II10AI of coarse fraction GM Silty gravels, gravel-sand-silt mixtures
COARSE- retained on No. 4 (4.75 min) sieve GRAVELS
GRAINED WITH RNES ~OC aayey gravels,: gravel-sand~ay mixtures :j
SOILS ..._-
More'than 50% ClEAN SW! Well.;.graded sands arid gravelly sands, little or no fiDes .,)
retained on No. 200 SANDS SP Poorly graded sands and gravelly and sands, little or no fines
(75 fdI') sieve" SANDS
More than 50% of coarsdraction SM Silty sands, sand-silt mixtures : . .
passes No.4 (4.75 mm) sieYe SANDS
WITH ANES "SC 'Oayey sands, sand.:.clay mixtures : .'.\ :
i ML Inorganic silts, 'Very fine sands, rock flour, silt yoi' clayey fine
sands -
SILTS AND ClAYS Inorganic clays of low to medium plasticity, gravelly clays, sandy
. liquid Umit SO% or less CL,
ANE-GRAlNED SOILS clays, silty clays, lean clays
50%0, more ~ OL Organic silts and organic silty clays of low plasticity
~ 200 ~ fAIl') In~)lganic silts, micaceous or diatomaceous fme sands or silts,
sieve 1 MH'
SILTS AND CLAYS ' ' elastic silts
Uquld limit greater than SO% CH Inorganic clays of high plasticity, fat clays
OH Organic clays of medium to high plasticity
Highly Organic Solis PT Peat, muck and other highly organic soils
(~~
\iI
TABLE 18-1-A-50IL CLASSIACATION CHART-(Contlnued)
CLASSIACATlON CRITERIA
Cu D6<Y'DIO Greater than 4
{DJCJ3
Cz = DIO X D60 Between 1 and 3
Not meeting both aiteria for GW
Atterberg limits plot below
"A" line or plasticity index
less tban 4
~tterl?erg limits plotting
10 hatChed area are bor-
derline classifications
requiring use of dual
symbols
Less than 5%, Pass No. 200 (75 1d11) sieve
More than 12% Pass N. 200 (75 1d11) sieve
5% to 12% Pass No. 200 (751d11) sieve
GW. GP, SW, SP
GM, GC, SM, SC
Borderline Classification
requiring use of dual symbols
Atterberg limits plot below
"A" line and plasticity index
greater than 7 -
Cu = D6<Y'DIO Greater than 6
CLASSIACATlON ON BASIS OF PERCENTAGE OF ANES
(DJO) 3
D X D Between I and 3
10 60
Not meeting both aiteria for SW
Atterberg limits plot below
"A" line or plasticity index
less than 4
Cz
Atterberg limits plotting
in hatched area are bor-
derline classificatioos
requiring use of dual
symbols
Atterberg limits plot above
"A" line and plasticity index
greater than 7
)(
411
'g
1:
~
~
..
III
0::
PLASTICITY CHART
For clas$IfIcat1on of fine-gralned soils and fine fract10n of coarse-gralned
solis
Atterberg Omits ploWng In hatched area are borderline classlflcatJons
requiring use of dual symbols.
Equation of A-4lne:
PI = 0.73 (LL-2O)
CH
A-Une
MH&OH
1
7r-----
4.-----
o
o 10
20
30
40
50
60
70
80
90
100
Uquld Umlt
Visual-Manualldentfflcatlon
3-329