Ordinance No. 83-03 I
CITY OF TIGARD, OREGON
ORDINANC F JO. 83- 0-3
AN ORDINANCE ADOPTING THE NATURAL FEATURES AND OPEN SPACE ELEMENT OF THE
TT(:AR11 COMPREHENSIVE PLAN; AND DECLARING AN EMERGENCY. _
WHEREAS, the City of Tigard finds it necessary to revise its Comprehensive
Pian periodically to improve the operation and implementation of that Plan;
and
WHEREAS, the Tigard Planning Commission has recommended the adoption of a
citywide Comprehensive Plan Element on Natural Features and Open. Space, after
holding a public hearing regarding the same; and
WHEREAS, the proposed Natural Features and Open Space Element has been
reviewed by the Committee for Citizen Involvement of the City of Tigard; and
WHE-R-F , the, proposed F,1 oment has been the subject of comments from the City's
N2ighb vrh C'a Planning Orl-1-ar zations (NPOi5) and individual citizens; and
WHEREAS, after considering the comments of the Planning Commission, the
Committee for Citizen Involvement, Neighborhood Planning Organizations and
individual citizens, the Council believes that the Natural Features and Open
Space Element of the Tigard Comprehensive Plan should be adopted in the form
set forth in Exhibit "A" attached hereto and, by this reference, made a part
hereof:
NOW, THEREFORE,
THE CITY OF TIGARD ORDAINS AS FOLLOWS:
Section 1: The Natural Features and Open Space Element of the Tigard
Comprehensive Plan, as set forth in Exhibit "A", consisting of a title page
and one hundred and three pages of text be, and the same hereby is, adopted as
a part of the city-wide Comprehensive Plan of the City of Tigard.
Section.- 2: In revising and compiling the Tigard Comprehensive Plan, the
Planning Director is authorized and directed to edit the Plan as necessary to I
provide a readable text; however, the Director shall not edit or change any
policy or implementation strategy adopted in Exhibit "A" and shall present all
portions of the edited Comprehensive Plan to the City Council for its approval.
Section 3:- In order to provide a uniform date for the effectiveness of this
series f Comprehensive Plan revisions to be adopted by the City Council in
JC,11 c-rge ,... iQ declared and this portion of the Comprehensive Plan
shall become effective on February 1, 1983
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PASSED: By unanimous vote of all Council members present, after being
read y number and title only, this 24 day of January , 1982.
Rec rder - City of Tigardd
APP::OVED: By the Mayor, this 24 day of Janus , 1982.
Gr'
Mayor City of Tigard
ORDINANCE NO. 83- 03
d'
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FEATURES
PEN SPACE
Comprehensive Flan Report
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CITY OF TIFA RD
WASHINGTON WuNi T,OREGON
ADOPTED BY CITY COUNCIL
DECEMBER 15, 1982
ORDINANCE NO. 82-81
NATURAL FEATURES AND OPEN SPACE
f C011111REHENSIVE PLAN REPORT
TIGARD PLANNING AND DEVELOPMENT DEPARTMENT
OCTOBER 1982
REVISED JANUARY 1983
REVISED JANUARY 19, 1983
REVISIONS MADE AS PER PLANNING COMMISSION PUBLIC HEARING JANUARY 18, 1983.
j;
CITY COUNCIL PLANNING COMMISSION
Wilbur Bishop - Mayor Frank lepedino - President
Join Cook Cliff Speaker
Tom Brian Donald Moen - ... ,
Nancie Stimler, Former Member Richard Helmer, Former Member
Ken Scheckla Mark Christen
Ima Scott Roy Bonn
Bonnie Owens
Deane Leverett
Phil Eden
TIGARD PARK BOARD MEMBERS
Ronald Jordon, Chairman
Robert Bellinger
Elizabeth Golden
Phil Hirl
Mary Ann McGinley
Mary Payne
Susan Sheriden
I
Pat Biggs
PROJECT STAFF
Bob Jean - City Administrator
William A. Monahan - Director of Planning and Development
Jeremy Coursolle - Associate Planner
F
Liz N lveW CV[t — Aobvciota". n«'l.2er
Frank Currie Public Works Director
Adrianne Brockman - City Attorney's Office
Patt Martin - Word Processing
Loreet, Wilson Officer Manager
ADOPTED BY TIGARD CITY COUNCIL JANUARY 24, 1983
ORDINANCE NO. 83-03
TABLE OF CONTENTS
Paye
I. INTRODUCTION i
11. PHYSIC.kL LIHI'IATI^r. K_r. N«TUR-kL _. nc'2D5 3
!t. F},UQQP iEil{is nllu wca.Loaauc.
B. Runoff Evasion and Ground Instability 12
C. Ground In Stability 14
III. NATURAL RESOURCES 22
IV. NATURAL AREAS 23
A. Vegetation 26
B. Wildlife 28 _
C. Special Areas 29
D. Historical - Cultural Resources 30
E. Scenery 30
V. AGRICULTURAL RESOURCES 31
VI. PARKS, RECREATION AND OPEN SPACE 31
A. Park System Classification 34
B. Park Standards 35
APPENDIX 51
A. , Hydrology 52
B. Floodplains and Wetlands 58
C. Geology 68
D. Groundwater 73
E. Soils 75
F. Existing Vegetation 77
G. Wildlife 81
H. Existing Parks, Greenways and
Recreation 88
I. Park System Development Charge 99
BIBLIOGRAPHY
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I. INTRODUCTION
D Statewide Planning Goals
This report addresses the concerns axpessed by LC..� €
;;3 e Agricultural Lands; #4 - Forest Land; #5 - Open Spaces, Scenic and �
Historic Areas acid Natural Resources; #7 - Areas Subject to Natural Disasters =
and Hazards; and #8 - Recreational Needs.
Goal #3 states: To preserve and maintain agricultural lands.
Agriculture lands shall be preserved and maintained for farm use, consistent
With existing and future needs for agricultural products, forest and open
space. These lands shall be inventoried and preserved by adopting exclusive
fart: -3e zones pursuant to ORS Chapter 215. Such minimum zones shall be
appropriate for the continuation of the existing commercial agricultural
enterprise with the area. Conversion of rural agricultural land to
urbanizable land shall be based upon consideration of the following factors:
(1) environmental, energy, social and economic consequences; (2) demonstrated
i.eed cousistent with LCDC goals; (3) unavailability of an alternative suitable
location for the requested use; (4) compatibility of the proposed use with
related agricultural land; and (5) the retention of Class I, II, III and 1V
soils in farm use. A governing body proposing to convert rural agricultural
land to urbanizable land shall follow the procedures and requirements set
forth in the Land Use Planning goal (Goal 2) for goal exceptions.
Goal #4: To conserve forest lands for forest uses.
Forest land shall be retained for the production of wood fiber and other
forest uses. Lands suitable for forest uses shall be inventoried and
designated as forest lands. Existing forest land uses shall be protected
unless proposed changes are in conformance with the comprehensive plan,.
In the process of designating forest lands, comprehensive plans shall include
the determination and mapping of forest site classes according to the United
States Forest Service manual "Field Instructions for Integrated Forest Survey
and Timber Management Inventories —Oregon, Washington and California, 1974."
Goal #5: To conserve open space and protect natural and scenic resources.
Programs shall be provided that will: (1) insure open space, (2) protect
scenic and historic areas and natural resource for future generations, and (3)
promote healthy and visually attractive environments in harmony with the
natural landscape character. The location, quality and quantity of the
following resources shallbeinventoried:
T.and noP_dpd or desirable fur open space;
< b. Mineral and aggregate resources;
r.
C. Energy sources;
d. Fish and wildlife areas and habitats; w
e. Ecologically and scientifically significant natural areas, including
desert areas;
f. Outstanding scenic views and sites;
g. Water areas, wetlands, watersheds and groundwater resources;
y h. Wilderness areas;
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i. Historic areas, sites, structures and objects;
® j. Cultural areas;
k. potential and approved Oregon Ld( LCa`L'Li)it tragi
}. Pctartial and approved federal wild and scenic waterways and state ,
scenic. waterways.
■ Wi,ere ,no cor£lictino uses for such resources have been identified,
such
resources shall be managed so as to preserve their original cenvironmentalWhere
and
conflicting uses have been identified the economic, social,
and programs
energy consequences of the conflicting uses shall be dete
developed to achieve the goal.
Goal #7: To protect life and property from natural disasters and hazards.
,a .. r loss of life shall not
Developments subject to damage or that coin. �esul_ in __ _
be planned nor located in known areas of natural disasters and hazards without
apprUplLatC safeguards Plans shall be based on an inventory of known areas
of natural disaster and hazard.
® Goal #8: To satisfy the recreational needs of the citizens of the state and
visitors.
The requirements for meeting such needs, now and in the future shall be
planned for by governmental agencies having responsibility for recreation
ivate
areas, facilities and opportunities: (1) in coordination with quality
enterprise, (2) in appropriate proportions and (3) in such quantity, q Y
and location as is consistent with the availability of the resources to meet
such requirements. State and federal agency recreation plans shall be
coordinated with
local and regional recreational needs and plans.
The roots of this document are planted in issues much broader than the title
might suggest. In essence, it is a plan intended to preserve the natural
characteristics and amenities of the greater overall community design. As a
bonus for this method of planning, a usable network of open spaces for
recreation and relaxation is identified and permanently set aside.
Growth in any community means a reduction of open space. Across the nation,
houses are covering agricultural land, & flood plains and wetlands are being
filled and built on, and a multitude of unique natural features are
lacebeing
exploited and lost forever. At the same time, growing populations p
an
increasing premium on the preservation of these same resources. The loss of
forest lands, scenic views, fi wildlife habitats, and the increasing pollution
adds to the need for preservation of our valuable resources.
tiiccs becwcG«
9_ _,«ti; -,,.a the envirnnmant are the result of the
These con
several components of urban development competing for the ase of our land
desires. The basic conflict is
resources to suit their specific needs and
between the individual land use rights and the broader interest of the entire
community. This is a major philosophical question for which there is rising
pressure to resolve. Tigard and other local governments throughout the land
are confronted with this issue on a daily basis. The solution undoubtedly
lies in the recognition of the necessity for maintaining an equitable balance
between the government's desire to protect the public interest and
individuals' , businesses' , and corporations wishes to use their land as they
please.
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this Plan recognizes the value of the natural environment, and strikes a
t and the indi
s is
balance between the broad public interes �vidual^�ig l
uide to land
accomplished through a process of using nature as tti .,-
n the Eoiiowing P
Lan nature's processes are used to determine
development. I' in
policy direction to "Itlu 2 irh
that continued develo�n' the pbestbCinte zsto of wall
_ the natural 'features of the corrununity and in
concerned.
for
ses. Any
re
The maps that are included ninin ththeseis pmapsort ashould review rthe vlarger ooriginals
one having questions concerning
located in the Department of Planning and Development in the Tigard City Hall.
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II PHYSICAL. LIMITATIONS AND NA'rIJKAL ..A...-_D$
ing
ard, takes
Human activity on the
surface °ndifferentf the h oto noucrd needs Band desires. if in
physical environment that
efforts in using the land are consistently st.ccessful (or unsuc. However, cessful,)
specific
may imagine that the earth is benign Cor hosty, into acti- with natural
location and an
characteristics ointlhumdetermineactivltthe outcome. Problems for
conditions and processes, jointly ni and even loss of life--occur
people--in the form of property damages, i . ury,
operly located.
when activities are impr "Natural Hazards should more
Hazards"
appropriately be entitled "Human .
FINDINGS
o The physical features which the make-up of any piece of land have a
y+ - direct relationship to the type and density of development which can be
operty
accommodated on that pr (carrying capacity)
Combinations such as
soils create severe development
steep slopes and unstable
increases
Excessive development in such physically limited areas greatly
the potential severity of landslide, earthquake damage, flooding, etc.
o Many portions of the floodplain area contain natural aspects such as
scenic areas and are valuable for open
significant vegetation, wildlife,
space and recreation.
serves an essential element in the process of runaff and
O degetatio. a .a urnj habitation of
erosion control, as well as for the protection aru
ved and replaced by buildings
wildlife. Nonetheless, it is too often remo
and impervious surfaces.
o_ Due to the general nature of soils and geologic mapping, site specific
analysis ogic hazards
is often necessary Yth,Pmse which rmine to a he pconstraint resence of gtoldevelopment.
and the severity of soL� p-� and
Such geologic hazards exist when certain combinations of slope, soil,
bedrock combinations, and moisture conditions render land unstable.
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o Earthflow and slump topography exist in hilly sections of the planning
area and are associated with poor drainage, shallow subsurface flow on
ground water and springs, and high susceptibility to erosion. Earthflow
and slump occurrences can destroy roads and buildings, and adversely
affect water quality. Mass iuoveitient has not resulted in any major loss of �
life or property thus far, because little in the way of urban development ,
exists on land with seriotis problems. ;
o Increased runoff and sedimentation from poorly developed hillsides can
require increased public expenditures for flood and erosion control and
storm water management.
o The City of Tigard had adopted a "Hillside Development Provision" within
the Sensitive Lands ordinance which requires additional review of those
developments. It
o The City of Tigard requires new developments to have a storm water runoff
plan to ensure against adverse effects such as erosion and sediment.
POLICY
3.1.1 THE CITY SHALL NOT ALLOW DEVELOPMENT IN AREAS HAVING THE FOLLOWING
DEVELOPMENT LIMITATIONS EXCEPT WHERE IT CAN BE SHOWN THAT ESTABLISHED
AND PROVEN ENGINEERING TECHNIQUES RELATED TO A SPECIFIC SITE PLAN WILL
MAKE THE AREA SUITABLE FOR THE PROPOSED DEVELOPMENT:
a. AREAS HAVING A HIGH SEASONAL WATER TABLE WITHIN 0-24 INCHES OF THE
SURFACE FOR THREE OR MORE WEEKS OF THE YEAR:
b. AREAS HAVING A SEVERE SOIL EROSION POTENTIAL;
C. AREA- SUBJECT TO SLUMPING, EARTH SLIDES OR MOVEMENT;
d. AREAS HAVING SLOPES IN EXCESS OF 25%; OR
e. AREAS HAVING SEVERE WEAK FOUNDATION SOILS.
IMPLEMENTATION STRATEGIES
1. The City shall designate on a map areas having physical limitation
(poorly drained, seasonally flooded, ground instability) and shall
incorporate these designations in the Tigard Community Development
W1C iuu RC l, shall l^p 4.rad.atcd ,
troc. r1^tiuenc E .
according to the distinct Characteristics of the constraints and ;
anticipated limitations.
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2. The City shall revise the sensitive lands section of the Tigard
Community Development Code to identify those areas that have distinct
constraints and limitations.
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3. The City shall cooperate with other agencies to help identify these
areas.
!:. The City of Tigard shall provide in the Community Development Code
that the City may require site specific soil surveys and geologic
studies where potential hazards are identified based upon available
geologic and soils evidence. When natural hazards are identified, the
City will require that special design considerations and construction
measures be taken to offset the soil and geologic constraints present
in order to protect life and property, and to protect environmentally
sensitive areas.
5. 1he Community Development Code shall not permit developments to be
planned or located in known areas of natural disasters and hazards
without appropriate safeguards.
The term "natural hazards," traditionally used in reference to such problems
�t floods,� as rl6ods earthquakes, erosion, etc. , is also inappropriate for another
v reason. The danger of a natural event or conditions depends upon ignorance;
it's a "hazard" when we don't know about it. On the other hand, if thele is
foreknowledge, the potential problem posed by the physical environment can be
carefully considered as a "constraint" or "limitation." For these reasons,
the phrase "physical limitations" (or physical constraints or environmental
limitations) is more accurate than "natural hazards" as a way of referring to
r the human problems posed by the physical environment of the Tigard area.
The traditional and more recent methods of coping with these problems mirror
this contrast in terminology between "natural hazards" and "physical
constraints." The earlier approach tended to involve a crisis reaction to a
severe event, with a focus on what was "wrong" with nature and efforts to
change the environment to suit human preferences. An integral part of this
approach has been government disaster relief and rehabilitation. While this
mode of response is not w- hout benefit, it has generally been shown to be
often inadequate and cost ineffective. Moreover, it contributes to increased
damages and injuries, in the final analysis, by indirectly encouraging more
improper use of land.
The newer method, embodied in the legislative trends at the federal, state,
and local levels the past twenty years, relies increasingly on land use
planning to, 'anticipate potential environmental threats and thereby control
inappropriate uses. This planning approach to physical constraints tends to
give .primary attention to the continuation of natural processes and minimizes
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human disruption, thereby lowering total costs to the community.
There are three major types of physicai constraints which L-Med to be addr _ccd
by land use planning in the Tigard area. They are:
1. Floodplains and Wetlands including areas having a high water table.
2. Ground Instability - including areas subject to earthquakes,
landslides, soil creep, settlement, subsidence, etc.
3. Runoff and Erosion - including areas subject to gullying and siltation.
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These three kinds of limitations to the use of land are distinguished by
characteristic differences in areas effected as well as natural processes
involved, and therefore in Cerins of the types of community controls necessary
to reduce potential problems. However, the natural physical processed
responsible for each of these constraints are fundamentally interconnected. L•'
convenience of focussing upon each separately should not obscure their
common origins, especially the basic roles of:
s;
1. Underlying geological deposits and processes,
2. Water in its many forms through the hydrologic cycle,
3. Surface soil properties,
4. Slope of the land surface, and
S. Vegetation
' Because of chese complex natural relationships, some land use controls
designed to deal with one group of physical constraints (eg. ; runoff and
erosion) may help reduce problems of another (ege , flooding).
A. Floodplains and Wetlands
Flooding and poor drainage together are the most obvious physical limitations
in the Tigard area, and i= is therefore both Tigard and Washington County have
floodplain ordinances. The regulation of land use in floodplains is
relatively recent, however, and illustrates how a fundamental shift in
treating physical limitations (natural hazards) is taking place.
FINDINGS
0 the objective of the City is to us,-- the detailed information gathered on
floodplains from the U.S. Army Corps of Engineers, and develop policies to:
1. Control development, as to not adversely affect the floodplain and
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floodway areas,
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2. Minimize the runoff-erosion impact of development on the surrounding
area and downstream properties, and
3. Emphasize the retention of a vegetation buffer along streams and
drainageways,_ to reduce runoff and flood damage and provide erosion
and siltation control.
o In addition, there is the issue of the cumulative effect of development
upstream of Tigard. Flood levels in Tigard will be substantially
determined by the controls exercised over development outside the plan
area, as well as inside Tigard`s Planning Area.
o The Fanno- Creek drainage system includes numerous small water courses.
"p The integrity of these natural drainageways is intrinsically connected to
the system's capacity to absorb excessive runoff and on subsequent flood
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levels. Often, however, water courses are altered to provide more usable
land. The resultant adverse impacts are detrimental to the entire
drainage system. i.e. , the storage capacity at the water course is
lessened and flooding occurs:
o besides the basic nerd to control development in flood prone areas, it was
found that public knowledge of floodplain hazards was lacking. Many of
the obstructions previously placed in rhe floodplain were the result of
either ignorance or overly optimistic attit-vr-G about potential flooding
problems. These obstructions (e.g. Main Street Bridge) hinder the flow of
high water and tend to increase flood levels.
o Proper administration of the floodplain areas relies heavily upon the
availability of adequate information upon which to assess the
environmental impacts of a project. The development, which creates the
need, should be responsible for providing the City with the necessary data
for making sound decisions. The burden is on the applicant to prove that
a project will not adversely affect the environment or create undue future
liabilities for the City.
® o The City of Tigard, with assistance from The U.S. Army Corps of Engineers,
has established an area designated within the 100-year floodplain.
o The City of Tigard has been accepted as an eligible area for the National
Flood Insurance Program, and as a result flood insurance will be available
to property owners in flood prone areas. The federal program, however,
requires the City to adopt an ordinance which meets certain federal
standards.
o The City of Tigard currently has ordinances, policies and standards within
the Tigard Community Development Code which provide adequate controls for
development within floodplain areas.
o According to the 1981 Drainage Master Plan Study conducted by CH2M Hill
for the City, flood levels of two to four feet higher than the existing
100-year flood plain may be expected if no corrective measures are taken.
Floods The Traditional Response
® The traditional, solution to flooding has been emergency actions to avoid
injuries and reduce property losses, and disaster relief. This approach has
emphasized structural solutions (e.g. dams, levees, channels) to prevent
damage from future- flooding. Unfortunately, this stria--;•iral approach has
often failed, because:
1. Floods often don't conform to the purpose of the structures or they
circumvent them over time.
2. The structures reduce the local flood � 7ard at the expense of
increasing the flood hazard either or both upstream and down stream.
3. A false sense of security stimulates even more development in risky
areas,
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The consequence is that floods continue to occur and losses are even more
catastrophic. Historically, flood losses in the U.S. have skyrocketed (a
cumulative total of $9 billion since 1936) despite massive expenditure on
flood control works.
The basic difficulty is that local governments allow people continue to locate
developainent in areas writh hibh flood risk. There is a large and growing body
Of technical research which documents that:
1. People are seriously uninformed about the flood risk.
2. People tend to be "grossly optimistic" about the flood problem.
Floods. - More Effective Methods of Reducing Costs
Growing out of investigations into the causes of rising flood damages is an
approach that emphasizes land use planning. It is the foundation of the
federal laws enacted in the 1960's, which provide for local restrictions on
fLoodplain uses in return for federally subsidized flood insurance, disaster
relief, and access to other federal programs. The land use planning approach
to flooding has three foci: �-
1. Floodplain management: restrictions on the use of land subject to
flooding.
2. Watershed management: restriction on activities within the drainage
basin that contribute to flooding (e.g. impervious surface controls,
wetlands protection, control of erosion during construction, etc. ).
3. Reliance on natural processes (minimal disruption of physical
processes): e.g. watercourses retained in their natural state.
In the -Tigard area, only one of these elements is currently ;;,zing fully
utilized. It is in the form of floodplain ordinance covering the 100-year
floodplain (see Floodplain Map). There are difficulties, however, with the
accuracy of the official maps delimiting the floodplain, especially along
Summer Creek and Red Rock Creek, as well as contradictions between calculated
flood elevations and their demarcation, but these problems can be resolved.
In addition, the U.S. Army Corps of Engineers has conducted a detailed survey
of the floodplain for the insurance rate maps of the Flood Insurance
Administration. This study includes a demarcation of the floodway that
portion of the floodplain with significant velocity of flood waters.
Additionally, the improved floodplain ordinance includes more stringent
controls in the floodway. Currently, the City of Tigard has adopted a
zero-foot Floodplain ordinance. obstructions in the floodway (e.g. Main
Street bridge over Fanno Creek) cause greater damage by raising lluud le ala. --
Much of the Fanno Creek basin (e.g. east side of Cooper Mountain) has not be
urbanized, and as it is developed flood elevations will rise (see Diagram
II). Increased runoff and erosion will mean that areas not now subject to a
100-year flood will be a risk in the future. Careful watershed management
could minimize the increase in flood heights. In the absence of good
hydrologic data, future flood levels will be difficult to predict. _A joint
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U.S. Calogic;l Survey - army Corps of Engineers rainfall-runoff study for the
Portland Metropolitan area has been developed to address this issue. Lower
Fanno Creek and the Tualatin River will also be affected by proposed flood
control works to control damages in D.ialatin.
Flood levels in Tigard will be substantially determined by the controls a
exercised over development outside the plan area. Urbanization of two areas
in particular, the west slope of Mt. Sylvania and the east slope of Cooper
Mountain, will have major impact on Summer Creek and Ball Creek,
respectively. Portland, Beaverton, Multnomah County, Washington. County, Lake
Oswego, and Clackamas County all have jurisdiction over portions of the Fanno
Creek basin above Tigard,
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Effective Approaches
Future flood losses in the Tigard area will be reduced by a combination of IN
actions, including:
1. Maintaining a strict City tloodplain ordinance which also includes the
amortization of structures in the floodway.
2. Watershed management (see Runoff and Erosion section).
3. Intergovernmental cooperation in floodplain and watershed management
in the Fanno Creek basin.
4. Public education (e.g. information about flood insurance, prominent
I
posting of flood heights, etc.).
Wetlands
Wetlands, watercourses, and other poorly drained areas outside the designated
100=year floodplain are inextricably connected with it. These areas serve
several natural hydrologic functions, including:
1. Temporary flood water storage.
2. Moderating flow of water over time (e.g. higher minimum flows).
3. Water filtration (e.g. sedimentation control) for higher water quality.
4. Ground water recharge.
The ground water recharge function is especially relevant in view of the fact
that the southwestern half of the plan area is part of the critical ground
water area defined by the state engineer in 1973. Within this area, ground
h water levels have been declining for almost thirty years. Prior to the s— e
restrictions on groundwater withdrawals, almost one-half (48%) of the total
annual pumpege was derived from recharge.
Much of the Tigard Plan Area is poorly drained, however the Wetlands Map
includes only the most severely wet-limited areas. Following U.S. Soil and
Water Conservation Sei ice practice, soils with a seasonal water table of 18
inches or closer to the surface were defined as wetlands. Therefore,
marginally _wet soils which cover Large areas (e.g. Aloha silt loam with
seasonal water table between 18" and 24") were excluded. Watercourses and
natural drainage swales, a large number of which no have permanent streams,
.o.o L.,nraa with r? - -F mora &-railed topoeraahv mans and aerial photos.
Many of these small streams have small floodplains of their own, posing
associated risks to develop-ment.
Effective Approaches
Effective use of these wetlands for storm drainage, flood protection, and
avoidance of other nuisances requires land use controls closely related to the
natural conditions of sites. For example, the characteristics of the flat,
-11—
poorly-drained areas between Hall Boulevard, Durham and Sattler Roads aie very
different frow the watercourses draining the northeast slopes of Bull
Mountain. In this context, surae general guidelines for the latter areas
should include:
1, Retention of natural watercourses (e.g. restrict fills,
channelization, etc. ).
2. Vegetation retention along adjacent slopes of drainageways.
3. Runoff-erosion controls on adjoining lands (a critical deficiency in
many wetlands ordinances, see section on Runoff and Erosion).
B. Runoff Erosion and Ground Instability
Runoff and erosion are intimately associated processes which can cause or
contribute to a wide variety of problems, especially in urban areas, including
siltation, flooding, ground water decline, and water pollution. Runoff is -
water flowing over the land surface and erosion is the downhill removal of
surface material.
Factors Affecting Runoff
There are three factors that effect the amount of water runoff and soil
erosion. These factors are the type of soil, the degree of slope to the land,
and the amount of vegetation on the site. Therefore, a site which is heavily
vegetated, which has nonerosive absorbant type soils and which has no slope or
moderate slope, will not create excessive runoff; in turn there will be no
t:rr,.=a.on. This, however, is not the situation in Tigard.
Soils which do not easily absorbwaterallow more water to flow over the
surface. Soils with high water tables or those not easily penetrated by water
(e.g. clay) have greater runoff. A large proportion of Tigard has high water
table and/or has relatively impermeable soil. With greater amounts of flowing
water, the velocity increases and erosion results.The degree to which a soil
is consolidated affects its erosion potential: unconsolidated material is
more easily broken down and removed by flowing water. Much of the Tigard area
is underlain by unconsolidated soils and geological deposits (see Ground
Instability, p. 15 and Geology Map).
Slope, or the incline of the ground surface, has a direct effect on runoff and
erosion because it increases the speed of the downslope movement. Water has
less opportunity to be absorbed into the soil. The water velocity and
quantity arc both increased- The nsZ1 ..o - � no and ciGn vai
steeper slopes. _..______-- _ !
effect
runoff and erosion and is the
_ .Vegetative cover has a direct el��.... o: ..-
fundamental reason why undisturbed sites in Tigard have less runoff and
virtually no erosion. Runoff is minimized by vegetation (generally, the more
vegetation the lower the runoff i.e. grass has less effect than heavy brush,
which in turn has less effect than forest) because:
-12-
I. Precipitation reaches the surface much more slowly, as it gradually
penetrates successive layers of foliage.
?_ marl nlant marerial on the surface is highly absorptive.
3. Snow and ice melt more slowly under vegetation (iincugii leaLless).
4. Once in the soil, som=a of the water is absorbed by the plants.
5. Runoff is slowed by surface debris and plant structures (e.g. stems,
trunks, twigs, etc. ).
Reduced storm water runoff volume and its slower movement mean lower erosion
potential. Vegetation also reduces erosion potential by stabilizing the soil
with its myriad roots. This is especially important on steeper slopes.
Effects of Urbanization
Urbanization and development tend to cause radical increases in runoff volume
.. and velocity and in associated erosion. These increases are due to:
1. the reduction and removal of vegetation.
2. The increased proportion of area covered by an impervious surfaces
(e.g. roofs, parking lots, streets, bare compacted ground such as
fills).
3. Building on slopes.
In an urban environment with little or no vegetation large volumes of water
are concentrated very quickly during a storm, and flow swiftly to the nearest
drainageway. Runoff under these conditions carries off as much as 85% to 90%
of the precipitation, in contrast to the 15% to 50% when the area was
undeveloped.
The resulting sheet, rill, and gully erosion strips the land of enormous
volumes of sediment, which can be as much as 1,000 times the natural amount.
Table I shows the amount of erosion found in a study conducted in Marland.
TABLE I
SEDIMENT VOLUME (tons/sq. mile/year)
Woodland 100
�.� Mixed Rural 300
Farmland
Light Development 10,000
Heavy Development 100,000
Erosion is particularly acute during the construction process; when the
vegetation is removed the soil is exposed. Site development also contributes
to increased erosion where natural drainage patterns are altered and runoff is
` channeled offsite without regard to existing drainageways.
-13-
;s di.-..usoad in the -section on floodplains and wetlsnds, the increased runoff
caused by urbanizatiou contributes to higher flood levels downstream.
Moreover, water which previously was released gradually to streams or entered
the groundwater reservoir, is no longer available during the dry months, so
that streamflow is lower then (which has an impact on water quality and
aquatic life) and groundwater levels are lower. Meanwhile, during the stormy
wet season, watercourses now carry runoff volumes for whLch they are no longer
suited, and their channels and banks are severely eroded. The large amounts
of sediments now carried by the streams also alter stream courses and, through
gradual filling, help raise the height of future floods.
Effective Approaches
Although large increases in runoff and erosion are an inevitable consequence
® of urbanization in the Tigard area, the destructive effects, and their costs,
can be minimized through the adoptinn of land use controls shown to be
effective elsewhere. These controls rely upon the demonstrated utility of
natural pros sses to achieve their ends. Major elements of the program
include:
1. Protection of vegetation, especially near watercourses.
2. Slope protection (e.g. slope - density restrictions, building
prohibition on steepest slopes, etc.).
3. Impervious surface controls (e.g. density restrictions).
4. Retention basins in same instances have been required on developed
sites to hold increases in runoff.
5. Control of construction practices which increase erosion.
C. Ground Instability
Recent Geologic History
Within geologically recent times, the Tigard area was subjected to two major
catastrophic events. Some ten to one million years ago small volcanoes
sprouted over what- is now the southeast and southwest Portland metropolitan
area. Rocky Butte, Mt. Tabor, and Mt. Scott east of the Willamette River and
Mt. Sylvania east of Tigard are all volcanoes of that period. Our legacy is
an underlying field of Boring Lava in the northeast part of the Tigard Plan
Area (see Geology Map). There may be lava tubes in this lava such as the ones
discovered at the new St. Vincent Hospital site in 1970. The potential
Ism (+.,, r
.-� 'f lora t+.hoc is a nnac hlo im—dlmPnt to major t-tructural
development. In view of the huge costs (e.g. million dollar proble*: at the
hospital) that could be incurred, such developments should t- preceded by
geologic investigation, including foundation borings and tests.
A truly devastating catastrophe engulfed almost the entire Tigard area during
the Pliestocene glaciation of only several thousand years ago. The Missoula
Flood was one of the most awesome, cataclysmic events in the geologic history
of North America. When water from a mammoth glacial .Lake in Montana broke
through its ice dam, it scoured much of eastern Washington and the Columbia
-14-
River Gorge before inundating the whole of the Willamette Valley to a depth of
approximately 400 feet. The principle entry-way of the water into the upper
:•Willamette Valley was the Lake Oswego gap, and the gravel deposits now mined
in the Durham area are the remains of the heaviest debris movea Ltirou—h rhe
con-tricrinn (see rpology Map). The sand deposits farther west alZg the
nnrth- aside of the Tualatin River are th2 finer seiiments deposited by the
Missoula Flood,
The problem which this program must address is unstable soil conditions. The
major problem is earthquakes and the inability to predict them. This is
important because earthquake induced ground movements constitute one of the
greatest potential physical limitations on land uses in the Tigard area,
because the following problems are associated with earthquakes: landslides;
subsidence, settlement, liquefaction, soil creep and mudflows.
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CIfY OF 11uAAD. PlNe1M6 •REF
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The specific causes of ground instability in Tigard are:
1. Underlying geological deposits;
2. Soil;
3. Slope;
4. Vegetative cover; and
5. Water as a lubricant and erosive force (e.g. undercutting)
Geological Deposits
Most of the geological deposits covering the Tigard area possess
characteristics which make them inherently unstable (see Geology Map). The
main problem is that the deposits are the unconsolidated sediments (Upland
Silt, Helvetia Formation, and Willamette Silt). The other two bedrock _
formations found in the area (Columbia River Basalt and Boring Lava) also have
minor shortcomings.
Columbia River Basalt underlies the entire plan area but is exposed only on
the slopes of Bull Mountain & Little Bull Mountain. It is usually deeply
weathered to a depth of perhaps as much as 200 feet with the upper layer
decomposed into a clayey soil with generally moderate limitations for
structures. Where the basalt has closely spaced jointing and open cavities
and is weathered, it is unstable on slopes steeper than 15%. Z, massive
landslide a half mile long occurred in Columbia River Basalt at West Linn when
I-205 was under construction a few years ago. Technically, it was a bedding
plane failure in the Vantage Horizon (a sedimentary deposit between layers of
basalt) and the dip (inclination of the bed) was only 3% - 5%. It is not
known whether the Vantage Horizon or similar weak planes exist in the Tigard
area. With the exception of L::e potential problems emphasized here, Columbia
River Basalt is generally stable and has few limitations as to use.
Boring lava is also relatively stable and has few limitations. An exception
is the previously mentioned possibility of lava tubes. Large scale
landsliding has occurred outside the Tigard area where this lava overlies the
Troutdale Formation, a circumstance which probably occurs here. Where the
surface of the unit is weathered deeply and the upper portion has decomposed
to clay, it is unstable when wet.
Most damaging landslides in the Portland area involve the wind-deposited,
unconsolidated losses (Upland Silt and Helvetia Formation) which in Tigard
occur on Bull Mountain & Little Bull Mountain. These soils are generally poor
for foundations, with moderately good strength when dry but unstable when
moist. They have poor compaction characteristics, for instance, and tend to
settle under moderately heavy loads. Slopes in these formations are
inherently unstable, with natural mudflows and landslides observed mostly on
slopes greater than 15%.
Willamette Silt, which mantles most of the Tigard area, is a water-deposited,
unconsolidated formation with characteristics similar to the losses: it is
r ,4 -17-
i
intrinsically unstable, especially when moist, and tends to lose its strength
when saturated. It is not so notorious as the losses, however, because of its
location at lower elevations where there are fewer steep slopes. Large scale
subsidence is a possibility (also for Young Alluvium) following severe decline
of the groundwater table due to massive withdrawals, but the actual potential
for this problem is not known at this time.
Young Alluvium, found along the geologically recent floodplain of the Tualatin
River, Fanno Creek, Summer Creek, and their major tributaries, has very severe
limitations. Aside from the fact that most of these areas have very high water
tables or are seasonally flooded, streamside locations face the problem of
bank erosion from undercutting. This unconsolidated formation is also
characterized by poor bearing strength. In a major earthquake, liquefaction
of this fine-grained, water-saturated unit could mean total failure of
strength and severe settling of structures and other loads.
Soils
The soils o€ the Tigard area (see Soils Appendix E) cover the geological
deposits with materials of diverse susceptibility to movement. Several
characteristics combine to determine their potential instability:
1. Slope
2. Perched Groundwater
3. Wetness
4. Erosion Potential
5. Poor Drainage
6. Thickness
7. Shrink-Swell Potential
8. Slow Permeability
9. Low Strength
A landslide rating system based on these L::zracteristics was developed for the
Lake Oswego area, by an engineering geologist. Applying this system to the
soils in Tigard shows that several areas have severe landslide potential and
several others have moderate potential (see Appendix). The characteristics
and conditions in Lake Oswego are similar to the conditions in Tigard.
Slope
The soil landslide potential ratings reveal that slope is generally the
critical factor in all cases. Moderate landslide potential is common for
soils with slope between 7% and 12%, and is generally severe for soils with
slopes exceeding 12%. Field investigations in Tigard have demonstrated the
existence of soil creep (very gradual downslope movement) on undisturbed sites
where the slope exceeds 25%. It should be kept in mind, however, that flat
areas immediately adjacent to a steep slope, both above and below, are subject
to the effects of a slope failure. The Slope Map of the Tigard Area shows the
concentration of steeper slopes in the following general locations:
1. Terrace escarpments above the Fanno Creek and Tualatin River
floodplains, _
� -18-
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2. Banks and slopes along watercourses and drainage swales.
® 3. Slopes of bull i•iountain and 1.zttle R,11 Mountain.
The slope of the surface alone can be a highly significant factor in
determining construction costs, as greater effort, design, and materials must
be used to ensure stability.
The following estimates of the effect of slope on house construction costs
were prepared by the Salem Home Builders Association:
% of Slope Added Cost of Home
®' 0-5% No added cost
6-8% 10 to 12%
8-12% 50%
12-15% 50-75%
18% Plus 100% and more
' Vegetation, especially trees, help stabilize the soil through its web ,
inoded sites,
roots. 0n slopes this is particularly important• liven .«ay .. rr
however, show that downhill earth movement is inexorable on steeper sloped,
with soil creep causing trees to develop bowed trunks near the ground.
Water is fundamental to ground instability, because it acts as a lubricant in
unconsolidated geological formations and in soils. The seasonal saturation of
otherwise susceptible areas is noteworthy. Flowing water in screams is also
responsible, under natural conditions, for bank erosion and consequent channel
modifications, particularly during infrequent heavy flood.
�u*
Earthquakes
The most severe earth movement which can reasonably be o:cpected in the Tigard
area would entail a major earthquake occurring when water has saturated the
ground (a lengthy freeze after the rainfall would wreak even greater havoc
should a seismic event take place).
With the exception of the liquefaction potential mentioned earlier,
earthquakes ,highlight already existing instability problems. There may be
another exception in the Tigard area due to the possibility of faults. The
Geology Map shows two probable major faults, one along the northwestern border
of the plan area near Scholls Ferry Road, the other transecting the area from
the Tualatin River on the southwest to the Pacific Highway to the northeast.
The data on which these lines are based consists of discrepancies in the
surface of the Columbia River Basalt underlying the valley. In the absence of
significant surface evidence, these "faults" may be considered inactive or, in
the words of the technical report, they are "questionable and may not exist."
If they are active faults, an earthquake along them could displace the ground
surface (horizontally or vertically) by a few feet or less.
The probability of major damaging earthquakes is high in the Fortland area,
and in this regard a recent general statement of earthquake authoritiesis
appropriate.
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' ". .. the short-term local seismic history is not in itself an adequate
base for estimating earthquake risk. Until we gain a better understanding
_ of earthquake processes and probabilities, due regard for public safety
demands that seismic hazard be considered high chruughouc wide areas, and
seismic zoning maps must reflect this." National Academy of Sciences, The
San Fernando Earthquake of February 9, 1971, Lessons from a Moderate
Earthquake on the Fringe of a Densely Populated ltagion.
In 1941, an earthquake with an intensity of IV on the Modified Mercalli Scale
(.see TABLE IX in Appendix) had its epicenter in Tigard. The November, 1962
earthquake felt over wide areas of Oregon and Washington had an intensity of
MMVII in the Portland area. This area is also subject to earthquakes having
their epicenters in Puget Sound, with a local intensity of MMVI. Duration of
shaking from distant earthquakes tends to be longer. According to recent
estimates for Portland the area earthquakes, the "100-year earthquake" (1%
annual probability) will have an intensity of between MMVII and MMX, depending
on the method of calculation.
r� In general, knowledge of earthquakes and ',ow to minimize their destructive
` impacts is still very limited. Despite warnings about the severity of the
risk, many businesses and individuals in other areas have moved into areas
devastated by earthquakes.
Human Activities
The natural potential for earth movements is often aggravated by human
activities, Which result in:
1. Oversteepening and removal of support of slopes by excavating.
2. Excessive loading (e.g. fills or structures).
3. Development on actively unstable slopes.
4. Vegetation removal on slopes.
5. Oversaturation of soils by sprinkling, runoff increases and
concentration, and changes in natural drainage.
Effective Approaches
Land use controls are needed to protect the public from the hazard of
landslides. Such controls would:
1. Restrict development and certain activities (e.g. excavation) in
inherently unstable areas, especially steep slopes. It is no
coincidence, for instance, that house construction costs in Western
Oregon generally begin to increase at about 7% slope, increase 506 at
12%, and double the cost when the slope is 18%.
2. Protect vegetation on slipes.
3. Minimize increased runoff and erosion as the area is urbanized (see
section on Runoff and Erosion).
u
1
� -21-
__ 7.,7. _
Table 4X.
SCALE OF EARTHQUAKE INTENSITIES W[TH APPROXIMATELY
CWRF.SPONDING ;MAGNITUDES
'maximum Magnitude corre-
Intensity Description of effects accerleration sponding to highest
characteristic effects of the ground intensity reached
I Instrumental: detected only be seismograph 10
3.5
II Feeble: noticed only by sensitive people 25
to
III Sight: like the vibration due to a passing lorry;
felt by people aL rest, especially on upper 4.5
floors 50
IV Moderate: felt by people while walking; rocking
of loose objects, including standing vehicles 100 4.3
V Rather Strong: felt generally; most sleepers are to
wakened and bells ring 250
4.8
VI Strong: trees sway and all suspended objects swing;
damage by overturning and falling of loose 4.9-5.4
objects 500
VII Very Strong: general alarm; walls crack; plaster 5.5-6.1
falls 1,000
4
VIII Destructive: car drivers seriously disturbed;
masonry fissured; chimneys fall; poorly con- 6.2
structed buildings damaged 2,500
to
IX Ruinous: some houses collapse where ground begins
to crack, and pipes break open 5,000 6.9
X Disastrous: ground cracks badly; many buildings des-
troyed and railway lines bent; landslides on 7-7.3
steep slopes 7,5000
XI Very Disastrous: few buildings remain standing;
bridges destroyed; all services (railways, 7.4-8.1
pipes and cable) out of action; great land- i
slides and floods 9,800 F
XXI Catastrophic: total destruction; objects thrown 8.1
into air; ground rises and falls in waves (maximum
known, 8.9)
III. NATURAL RESOURCES
With the exception of aggregate resotirces, there are nu known mineral
resources or energy resources in rhe 't'ieard Detailed Plan Area. Quarry Rock
(Columbia River Basalt and Boring Lava) is found here, but is so widely
available elsewhera and poorly located for mining ia Tigard, that it cannot
reasonably be considered a source of supply (see Geology Map).
FINDING
o Currently, there are extensive rock and gravel extraction areas located to
the north and west of Tigard's planning area but within Beaverton and
Washington County.
o There are no known mineral or aggregate resources within the Tigard
Planning Area. (See Washington County Resource Document, Volume I, 1982. )
POLICY
3.3.1 THE CITY OF TIGARD SHALL SUPPORT THE EFFORTS OF WASHINGTON COUNTY,
BEAVERTON AND THE METROPOLITAN SERVICE DISTRICT TO ENSURING THE
AVAILABILITY OF THE ROCK MINERAL RESOURCES.
IMPLEMENTATION STRAGEGY
I. The City shall encourage those jurisdictions regulating rock extraction to
closely monitor the relationship between the demand for the resource and
the amount of land planned for rock and gravel extraction and processing.
The gravel deposit in the southeast portion of the plan area near Durham has
been quarried by Washington County. The gravel was relatively poor quality
and was, therefore, being used only for such purposes as gravel roads and
shoulders, oil rock, sand, and rip-rap. Most of the site has been excavated,
and at the present extraction rate, the remaining supply will last until
2005-2010. However, the northern boundary of the deposit is uncertain, so its
full potential is unknown.
A belt of potential fill sand is found in the terraces above the Tualatin
River, south of Durham Road in the broadening belt extending from 92nd on the
east past Pacific Highway on the west.
The Portland MetropolitanAreafaces future difficulties in obtaining adequate
supplies of sand and gravel, since the bulky material is expensive to
transport any distance and urbanization has foreclosed mining deposits close
to the City. Whether gravel extraction should be extended further in the
Durham area, and quarries developed in tie sand deposits; are questions which
require more detailed information before they can be answered. The Oregon
`Department of Geology and Mineral Industries and the former Columbia Region
Association of Governments conducted studies of the physical and economic
aspects of sand and gravel deposits in the Portland area.
-22-
Energy
Resources and Sites
Available information indicates that the Tigard Planning Area does not contain
any potential energy reseurcos, or sites.
Coal - No deposits have been tound and the geology of the area is very
unfavorable to its occurrence.
Oil and Gas - Deep drilling in Northwestern Oregon has failed to locate
even significant shows of petroleum or natural gas. The Texaco
Cooper Mountain 1 well was the closest to the plan area and found
gassy salt water. The Western border of the Tualatin Basin has
some structural and tratigraphic features that warrant further
investigation, but there is apparently slight prospect elsewhere
in the Tigard area.
Geothermal - The closest known Geothermal Resource Areas are situated near
the crest of the Cascades.
Solar - The design and economics of large-scale solar power plants are
still at the rudimentary stage. Only general, large areas of the
state have been suggested as potential sites for solar electric
power generation, and these are in parts of Oregon with greater
sunshine than the Tualatin Valley.
Wind- Commercial scale wind power generators have also not yet been
developed. Potential sites include wind-prone areas such as the
coast, rather than the relatively calm Tualatin Valley.
Thermal Power Plants- No conventional or nuclear power plants are
current IT planned in the Tigard area, nor will any conceivably be
suggested in the future, according to officials of Portland
General Electric and Pacific Power and Light.
It' NATURAL AREAS
Within the past several years the value of the wildlife and natural vegetation
has been recognized by an increasing proportion of the public, especially with
regard to their place in the urban environment. Large numbers of people enjoy
the overall presence of birds, the color of wildflowers, or the sounds of
animals, while other more actively engage in nature photography, berry
picking, or bird watching. Urban natural areas are also a part of the outdoor
classrooms for teaching children about the living world around us. The ready
accessibility of natural areas to citydwellers reduces the necessity for
individuals or families to travel many miles by car in order to appreciate the
wonders of wild life. Natural areas, especially vegetation, also provide
visual amenities to a community by softening the impact of the man-made
environment. All of these contributions of natural areas function together to
help blur the distinction between the City and the country, to bring into the
City some of the most attractive features of the country.
23
i
I
FINDINGS
o There are a variety of plants, animals and water tow! with the Tigard
planning area which greatly add to the ,L,atit- of life thin the
community.
o Each species requires a cc:aplex and often, a narrowly specific set of
conditions with respect to food, water, and vegetative cover or other
natural features necessary for escape and reproduction.
o The significant plant communities and animal habitat areas are the
riparian vegetation adjacent to the water resources in the community, and
various stands of timber and brush.
o Development adjacent to existing wildlife areas can adversely effect these
areas and in some instances can virtually eliminate these needed wildlfie
habitat areas.
o Vegetation contributes to the aesthetic quality of the community.
Vegetation controls erosion, absorbs sound, and moderates temperatures.
It also affects the flow and moisture content of the air, reduction of air
pollution and glare, and softens the impact of the urban environment.
POLICIES
3.4.1 THE CITY SHALL DESIGNATE THE FOLLOWING AS AREAS OF SIGNIFICANT
ENVIRONMENTAL CONCERN.
a. SIGNIFICANT WETLANDS;
b. AREAS HAVING EDUCATIONAL RESEARCH VALUE, SUCH AS GEOLOGICALLY AND
SCIENTIFICALLY SIGNIFICANT LANDS; AND
C. AREAS VALUED FOR THEIR FRAGILE CHARACTER AS HABITATS FOR PLANS,
kr' ANIMAL OR AQUATIC LIFE, OR HAVING ENDANGERED PLANT OR ANIMAL
SPECIES, OR SPECIFIC NATURAL FEATURES, VALUED FOR THE NEED TO
PROTECT NATURAL AREAS.
3.4.2 THE CITY SHALL:
a. PROTECT FISH AND WILDLIFE HABITAT ALONG STREAM CORRIDORS BY
MANAGING THE RIPARIAN HABITAT AND CONTROLLING EROSION, AND BY
REQUIRING THAT AREAS OF STANDING TREES AND NATURAL VEGETATION
ALONG NATURAL DRAINAGE COURSES AND WATERWAYS BE MAINTAINED TO THE
MAXIMUM EXTENT POSSIBLE,
b. REQUIRE: THAT DEVELOPMENT PROPOSALS IN DESIGNATED TIMBERED OR TREE
AREAS ;BE REQUIRED TO BE REVIEWED THROUGH THE PLANNED DEVELOPMENT
PROCESS TO k1INIMIZE THE NUMBER OF TREES REMOVED; AND
" c. REQUIRE CLUSTEP TYPE DEVELOPMENT IN AREAS HAVING IMPORTANT
WILDLIFE HABITAT VALUE AS DELINEATED ON THE "FISH AND WILDLIFE
HABITAT MAP" ON FILEN AT THE CITY.
P
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IMPLEMENTATION STRATEGIES
1. `lhe City shall consider the inclusion of an adequate amount of land
adjacent to a floodplain or drainageway for dedication to the City's
natural greenwajte!n, which allows the area to continue to support
Jy ��y., �..
existing habitats. ':
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2. The City shall, encourage through the Planned Development Process,
the retention of large, varied habitat areas on private and public
lands including inventoried plant and animal communities.
.3 The City shall review all development proposals adjacent to wildlife
habitat areas to ensure that adverse impacts on any wildlife habitat
areas are minimized, and if need be, request that other federal,
state, and loral agencies review the development proposals.
4. Where there exist large or unique stands of trees or major vegetation
areas within the planning area on undeveloped land, the City shall
ensure that development proposals do not substantially alter the
character of the vegetation areas through the Planned Development
Process and the "Tree Cutting" section of the Community Development
Code.
Vegetation and Wildlife
Wildlife is dependent upon natural vegetation for food and shelter, and in
some cases for protection. Since each animal species has special
requirements, the greater the variety of habitats (and natural vegetation,)
the more different kinds of animal life can be found in an area. There are
four general kinds of habitat which are particularly important for a diversity
of wildlife:
1. Woods (which provide cover for deer, for example).
2. Brush (an often mistakenly-undervalued wildlife resource of great
importance as cover for many animals).
3. Riverside areas (known as Riparian)
4, Wetlands (lands seasonally wet or with water close to the surface).
The riverside areas and wetlands are the most critical for a wide diversity of
animal life because they are places where extremely different kinds of
environments (aquatic and terrestrial) interface. Non-living components of
the habitat can also be of great significance for some animals. Dead standing
trees, or snags, are particularly valuable. In the Tigard area there are at
least two mammals and nine birds (e.g. wood duck, screech owl), which are
totally or heavily dependent on snags.
on, urbanization can destroy virtually all natural
`a
Without special protecti
vegetation and associated wildlife. As an area develops, most of the original
vegetation is cut or radically altered. This most obvious when heavily wooded
C., areas are replaced by structures and streets. Even where many trees are
retained, however, the undergrowth is usually removed and replaced by closely
clipped la-urns, weeded gardens, and exotic shrubs - all of which fail to
E-
-25-
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provide the kind of habitat required by most animals. If some natural
environment is rotained, the increased population of adults, children, pets
and autos may still spell doom for the nnrural environment. Wildflowers and t
berries, for instance, may not be able to withstand trampling and heavy
picking, and dogs and cats will harass squirrels and herds. Narar-reiatrd
recreation demands may degrade the natural characteristics of riparian ;
habitat. Wetlands and aquatic habitats suffer from increased water pollution g
(septic tanks, street oil, etc.) runoff and erosion, siltation, and lower
flows during the dry season.
A. Vegetation
At present the Tigard area possesses only remnants of its original
vegetation. When pioneers settled in the area about 125 years ago (1852),
much of Bull Mountain & Little Bull Mountain had recently been burned, and the
vegetation consisted of a mixture of woodlands and grasslands. Characteristic
plants were (and still are) found in certain locations depending upon the soil
types, water availability, and exposure to the sun (e.g. north or south facing
slopes). Dominant tree species include:
A. Conifers (needleleaf evergreen)
1. Douglas Fir - Very widespread, moist, well-drained sites and
moderately dry sites
2. Ponderosa Pine - drier sites, largely in the north central area
3. Western Red Cedar - moist sites, near watercourses, northern exposure.
B. Deciduous (broadleaf)
I. Oregon White Oak - generally drier sites
2. Oregon Ash - moist sites, especially along watercourses
3. Red Alder - very moist sites, especially along watercourses
4• Cottonwood - along watercourses
5. Willow along watercourses
6. Big Leaf Maple - moist sites
Less common plants, and those less conspicuous or part of the understory
include, for example:
(1) Madrone (broadleaf evergreen) uncommon in Tigard
(2) Dogwood - small deciduous understory tree with showy flowers in
season (Spring).
(3) Wild Rose
(4) Poison Oak
(5) Blue Elderberry
(6) Sword Fern
�,., (,7) °gid H-citleber_y
(8) Salal
(9) Oregon Grape
(10) Vine Maple
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EXISTING VEGETATION
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there is a possibility that the Tigard area has plant species which
en
judged rare or endangered by botanist specialists, as was found tobehave
base
in Lake Oswego, '!too have been mentioned in this connection the marsh
trillium (Oregon list) and fawn lily (National list) - but without careful
inspection by field botanists t;;eir occurrence here cannot be known with
certainty,
Remaining areas of relatively natural terrestrial vegetation have: been mapped
for Tigard, using the following broad categories.
(1) Coniferous Forest
(2) Deciduous Forest
(3) Mixed Coniferous - Deciduous Forest
(4) Brush
(5) Meadow (may overlap Marsh)
(6) Marsh
B. Wildlife
There is still a surprising diversity of wildlife likely to be found in
Tigard. Among the terrestrial or partly terrestrial species (including birds
and amphibians) are:
(1) Deer - woods (e.g. Little Bull Mountain), riparian
(2) Fox field, brush
(3) Mink - riparian
(4) Weasel - riparian
(5) Beaver - riparian (e.g. FannoCreek)(6) Raccoon - riparian (e.g. Summer Creek)
(7) Great Blue Heron - riparian
(8) Belted Kingfisher -riparian
Aquatic habitat (e.g. streams, lakes, ponds) in ligard has been seriously
degraded over the past thirty years as the western suburbs of Portland have
rapidly developed. The very severe sewage Pollution of Fanno Creek has been
substantially reduced by the completion of the interceptor line to the new
Durham Treatment Plant. Water quality in the Tualatin River is also improving
as a result of low flow augmentation of water stored behind Soggins Dam, and
has been considerably better when the Rock Creek Treatment Plant in 1977.
Even with these improvements, however, problems with
temperatures and low flows, turbidity, siltation, and seasonal high water
lution will continue
to some extent. It was once possible to catch 12" - 1 8" trout in Fanno Creek,
as difficult as that is believe today; and 'both Fanno Creek and the
Tualatin River were famous for their prodigious number of crayfish which
helped stock Portland restaurants. It is questionable whether these days will
ever be ��ack, but a local abundance of tasty aquatic species seems possible.
At the present time, the Tualatin River is known to harbor a number of
warm-water game fish including bass, crappie, catfish and bullhead.
also are some chinook and coho salmon and cutthroat and stee There j
may be migratory o lyl, lhead trout (which
g y n I iw detailed inventory has been conducted on Fanno
Creek since the sewage was diverted. -In addition
crayfish (also f.^.:�.,�i ; , .L_ tion to car p, sucker; and
y - -•• ���C Tualatin River), there are probably crappie,
bullhead, and perch in Fanno Creek, and even trout.
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Effective Approaches
Much, if not most, of the remaining natural area i❑
disappaar as the community approaches 1'gard could completely
possible PP full development. However,
to preserve significant portions of the natfjral it is
despite this general trend. To do so the community will need to: found nere
l• Protect existing natural vegetation
wherever possible (e, (trees, shrubs, and grasses)
g. in parks) especially along watercourses.
2. Use native plants in landscaping.
J. Leave wetlands and
riparian areas in their
discourage filling, channelization, drainage_ etc.). state (e.g.
4. Control runoff and erosion to protect aquatic habitat and wetlands.
5• Provide corridors for wildlife movement (e
System). .g, as through the Greenway
6. Leave non-hazardous snags along streamz and in wetlands.
Many of .thesemeasures to
useful Provide future natural areas and values also
accomplish another
functions as outlined elsewhere
on Runoff and Erosion, Scenery, Ground Instabilit
(e.g. see sections
Instability, etc.).
C. Special Areas
In addition to the general policies to help protect natural vegetation and
P areas have been suggested by specialists for
through fee purchase if necessary. These areas were:
.singled out for preservation,
priority attention because oi:
2) their relative uniqueness.1) their particular vegetation
as the cost of preservation will, of course Other factors such
and wildlife values, and/or
six areas which were identified are the: ' ai'o have to be considered. The
1. Summer Creek marsh
(east130th and south of
This unique 12 acre marsh-pond Scholls Ferry
complex was su ested for y Road. -
servon
by both the district field biologist for the state Department ofati Fish
and Wildlife and a field biologist with the Nature Conservancy.
2• Forested Northeast slopes of Bull Mountain.
Slopes contain some large Douglas Fir which The heavily-wooded steep
and three feet in diameter. are up to 100 feet tall
sites outside the The site connects
Plan area. with other similar
It was recommeded
the Nature Conservation Biologist, for preservation by
F
3• Summit of Little Bull Mount
under
undergrowth a`n• !his area has a heavily-wooded with
g providing cover for a variety l raccoonof animals including c]eer,
', � pheasant
L -29
4. Willow Brook, lying south of Durham between 108th and 113th. A wooded
and brushy minor creek in the floodplain, providing access to the
Tualatin River. It 's protection was recommeded by the Nature
Conservancy Biologist,
5. Tualatin River bank between 108th and Coot, lark. This is an important
riparian habitat which was recomuaetided fur protection by the State
Field Biologist.
6. Fanno Creek marsh at Tigard Street, which was recommeded for
proservation by the (State Field Biologist).
D. Historical/Cultural Resources
The overall character of the community, is a product of its past. As a
community develops it should not discard its past for the sake of the future.
The John Tigard Home is the only remaining structure of local and national
historical significance. It is listed in the National Registry.
The Tigard Area Historical and Preservation Association (TAHPA), a nonprofit
organization committed to he preservation and maintenance of valued historical
objects and landmarks, is currently in the process of relocating the John
Tigard Home to a usable and available site. After restoration and renovation
the Tigard Home will host the proposed Tigard Museum which will be open to the
public and display many valued artifacts which highlight Tigard's historical
past.
Another structure identified as historically significant, and documented in
the "Statewide Inventory of Historic Sites and Buildings", is the so called
Water Tower (also referred to as the Windmill) situated along 121st Avenue and
S.W. Lynn Street. It was recently donated to the City and has been earmarked
for restoration and/or renovation.
E. Scenery
An inventory conducted by the City of Tigard (and after consulting the "Orion
State Parks System Plan") revealed that there are various scenic views and
sites and/or waterways, as defined in Goal #5, that exist in the Tigard
Planning Area.These include:
I. The summit of Little Bull Mountain;
2. The summit and eastern slopes of Bull Mountain;
3. The view of the Tigard area from Little Bull Mountain and Bull
Mountain, which include views of Mt. Hood;
4. The view of Mt. Hood from the Hillview area; and
5. The view of the Tigard area from the Tigard Triangle, looking to the
west.
+�- -30-
Fo-
V. AGNICUL'lURAL RESOURCES
�
-- Art tc;u LLural Resources
Tigard's heritage is linked to its agrarian past and maintaining some record ;
and vestiges of this disappearing history should be a community concert:. In
addition, farm land ties into the pattern of open space set forth in the
community's design objectives.
Until the early 1950's, Tigard primarily remained an agricultural community.
However, since the conversion to urban uses began, increasing amounts of farm
land have been converted to other uses.
Tigard lies within the Urban Growth Boundaries established by Metropolitan
Service District. Population projections and land use needs studies show that
all of the land inside the Tigard Urban Planning Area will be needed for urban
development within the year 2000 planning period. Under these circumstances,
preserving large tracts of farm land would place an unnecessary burden on the
community to increase densities elsewhere to ccpensate for the loss of needed
residential space. An additional consideration is that most of these
remaining parcels are not large enough to be economically viable.
TABLE I
YEAR POPULATION NO. OF DEVELOPED ACRES NO. OF NEEDED ACRES
1980 14,286 4,871.35 Residential - 906.23
2000 33,400 Corunercial - 195.30
Industrial - 277.57
TOTAL - 1379.10
TOTAL AMOUNT OF LAND WITHIN TIGARD URBAN PLANNING AREA - 6393.60 ACRES
Forest Lands
There are no lands within the Tigard Urban Planning Area designated for
commerical forest land. Therefore, LCDC Statewide Planning Goal #4: Forest
Lands does not apply to Tigard's Comprehensive Plan.
VI. PARKS, RECREATION AND OPEN SPACE
Rapid growth in a community like Tigard tends to diminish the availability of
..a;
land for recreational purposes. Increasing land values are a cc���Y ......=n..bg
factor and tend to inhibit acquisition of quality recreational land,
_b
31
Simultaneously, regional growth containment boundaries have been drawn,
increasing the pressure for development inside the boundaries. Tigard is
located within the growth cnnrai_nment araa. 'Therefore, increased demands for
development can be expected, resulting in even greater pressures to consume
available open space.
While the supply of land decreases, the need for recreational space
increases. An urgent need, therefore, exists to provide these facilities by
devising a method for financing a land acquisition and development program
that can compete with the pressures of development. Since new development
will generate the increased demand, such a financing method must look toward
this new development bearing its share of the financial responsibility.
FINDINGS
o In Tigard, public and private organizations can play an important role in
providing leisure and recreational opportunities and cultural activities.
o Many of the Tigard School District sites provide recreational needs not
found within many of Tigard's parks.
o Small parcels of unbuildable land resulting from urbanization can provide
mini—parks or- landscaped areas.
o A properly planned and managed system of open space and recreation lands
can reduce the impact of urbanization and serves the leisure and aesthetic
needs of all residents. The system needs to recognize the relationship
between urban uses and the natural character of the land and drainageways.
o The community has indicated a desire for open space linkages which follow
scenic routes and connect parks, schools, playgrounds, shopping areas,
other public sites, and residential areas.
o The City needs to develop an adequate system of open space, recreation
lands, and facilities to retain and improve livability of the community.
• In the process of planning for a park and recreation system, it is
necessary to classify the individual components such as neighborhood parks
and the greenway which will or could comprise the park system. In
addition, the establishment of a reasonable acquisition and development
program requires a listing of priorities and minimum levels of service to
be provided. The actual development of such a system requires relating
the provision of facilities and services to the particular needs and
recreation desires of the residents to be served.
,1
POLICIES
3.5.1 THE CITY SHALL ENCOURAGE PRIVATE ENTERPRISE AND INTERGOVERNMENTAL
AGREEMENTS WHICH WILL PROVIDE FOR OPEN SPACE, RECREATION LANDS,
FACILITIES, AND PRESERVE NATURAL, SCENIC, AND HISTORIC AREAS IN A
' MANNER CONSISTENT WITH THE AVAILABILITY OF RESOURCES.
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3.5.2 THE CI'T'Y SHALL COORDINATE WI'T'H THE SCHOOL DISTRICTS TO DEVELOP
RECREATIONAL FACILITIES.
3.5.3 THE CITY SHALL DESIGNAIE 'THE 100-YEAR FLOODPLAIN OF FANNO CREEK, LT'S
TRIBUTARIES, AND THE 'IUALATTN RIVER AS GREENWAY, WHICH WILL BE THE
BACKBONE OF '!HE OPEN-SPACE SYSTEM.
3.5.4 THE CITY SHALL PROVIDE AN INTERCONNECTED PEDESTRIAN iUirIlATH
THROUGHOUT THE CITY.
IMPLEMENTATION STRATEGIES
1. The Tigard Community Development Code shall require land divisions and
major developments to set aside, dedicate land, or pay a fee in lieu
of land aside based on standards, and the standards shall provide for:
a. An area composed of developable lands which may provide active
recreation space; and
b. Adequate passive open space to protect natural resources at the
site and protect development form hazard areas.
2. The City shall permit land which is set aside within developments to
remain in private ownership provided:
a. Portions art! sufficiently improved and maintained to offer active
recreation opportunities;
b. They do not interfere with the continuity of or access tG adjacent
greenway lands; and
r
C. Easements transferring development rights are dedicated to the
public.
3. The Tigard Community Development Code s11-aall indicate flexible design
options which mitigate the impacts of required open space and
recreation land dedication or reservation.
4. The City shall designate natural park areas within a Tigard Master !�
Parks Plan. The areas will have unique physical or aesthetic features
and do not have to be developed to be of recreational use to the
community. Area; which have special physical features such as natural
watercourse, significant vegetation, scenic vistas, and that provide
habitat for wildlife will be considered.
5. Open space and greenways shall be used to enhance the accessibility to
schools and parks by establishing a safe and well-marked trail system
which will also connect with significant regional trail systems.
b. Park classifications and standards shall be adopted and a program
developed for acquisition and development of a park and open space
system to ensure an adequate supply of usable open space and
recreational facilities, directly related to the specific needs of the
local residents.
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` 7. Streets and drainageways shall be combined with a parkway or greenway
concept to permit linkages between open spaces; residential areas,
recreation lands, and centers of economic activity.
8. The City shall continue to seek assistance n: volunteer groups to
assist in developing and maintaining parks,
5. Master pians for each park shall be developed. 'Illese plans shall
identify park facilities for each park and ensure that parks are
developed so as to promote safe and aesthetically pleasing
environments while minimizing the harmful effects of noise, air
pollution, vehicular traffic, and other negative aspects of urban life.
10. The City shall continue to implement the adopted bike plan by
requiring development adjacent to the Greenway to construct their
portion of the bikepath system.
11. To augment the scenic benefit of the greenway, the City shall
establish the major vehicular transportation routes as scenic or
visual corridors. The Park Board should plan and initiate a program
(through public and private cooperation) for corridor landscape
preservation and/or improvement.
PARK SYSTEM CLASSIFICATION
In the process of planning for a park and recreation system, it is necessary
to classify the individual components such as neighborhood parks and the
greenway which will or could comprise the park system. In addition, the
establishment of a reasonable acquisition and development program requires a
listing of priorities and minimum levels of service to be provided. The
actual development of such a system requires relating the provision of
facilities and services to the particular needs and recreation desires of the
residents to be served.
The following standards and policies are intended as guides for the
development of a park system which relates to development as it occurs and to
the varied recreational needs of the City's residents. However, specific
needs and desires differ from neighborhood to neighborhood. In addition, the
needs of future residents cannot be accurately projected. For these reasons,
the pace uevcivplilei,t uisl,ii.crs see Open Space Map) were established.
The districts were selected based on present development patterns, the
selected park standards, and by using major streets as access barriers. The
boundaries are not permanent and may be adjusted in the future if
circumstances change. The purpose of the districts is to provide service
areas where the amount and types of recreational facilities can be planned and
eventually provided based upon the specific needs of the people residing there.
Classifications
1. Mini Parks
2. Neighborhood Parks
3. Community Parks
4. Large Urban Parks
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77
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Regional Parks
- ay be combined
6. General Open Space (Preservation Oriented m )
A. Scenic Pathways I
B. Landscaped Areas
C. Natural Preserves 4
s 7. water Oriented Sites
A. rA. Cling
B. Boating
C. Swimming
8. Special Use Areas
A. Play and Ball Fields
B. Courts (tennis, basketball)
C. Ranges (rifle, bow and arrow)
D. Sw- twaiitg Pu0i3
E. Trails
F. Sports Complex (two or more of the above)
G. Golf Courses
9. Cultural Facilities
10. Historic Sites
11. Activity Centers
PARK STANDARDS
The size and acres per 1000 population figures are set at an a,-,arage desirable
level for each component. The overall desirable level set by these standards
is 10 acres per 1000 people which is approximately the present level provided
within the City. In combination, these standards constitute an ideal park
system.
Basic Assumptions:
1. The ideal park system is intended to serve as a guide and will be used
:4 to evaluate decisions on the ongoing process of parks development. it
will also serve as the basis for es. ' '.shing a systems development
program.
2. Due to economic constraints or population characteristics the ideal
may never be reached. However, policy decisions should be based on
priorities , chat are economically feasible, but also directed toward
the established ideal system.
3. The assumptions, data, criteria and policies should be periodically
reviewed to account fog iiianges in circumstance.
The park acreage standards are set for lands available to the general public,
and owned or otherwise controlled by the City or a cooperating public agency.
They do not include:
I. Public School property (not available for active recreation).
2. Special areas (pathways, cemeteries and golf courses).
3. Private or voluntary agency lands and facilities.
4. Vacant undeveloped land not under ownership or control of the City.
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Standards
1. MINI PARKS
Purpose: :o supply a minimum of bark land to serve as a "Back Yard"
for isolated areas or where density, lot .,ize, and/or income
conditions deny availability of such facilities; or where access to
neighborhood parks is restricted; or to provide landscaped sitting
areas in the commercial core of the city.
Size: 2500 sq. ft. to 1 acre
I
Acres/People: 1 acre/1000 people
Service Area: 1/4 mile radius
Location: Determined by need
Facilities/Activities: Play equipment, hard surface for wheeled toys,
sand area, benches and tables and trash receptacles shall be
provided. Benches, vegetation, and trash receptacles shall be
provided in commercial area parks.
2. NEIGHBORHOOD PARKS
Purpose: To serve as the neighborhood center for active and passive
' recreation.
Size: 2 to 5 acres
Acres/People: 2 acres/1000 people
Service Area: 1/2 mile radius
Location: Should be centrally located and away from major
thoroughfares. Easy visibility and access from surrounding residents
and public right-of-way should be considered.
Facilities/Activities: Should be individually designed by shall
provide open play areas, picnic area, drinking fountains, and trash
receptacles. Consideration should be given to provision of playground
facilities, natural areas, fencing, lighting, irrigation and ease of
maintenance. Additional facilities should be based on the
recommendations of neighborhood residents and the City Park Board.
3. COMMUNITY PARKS
Purpose: To provide facilitieswhich generally cannot be provided at
the neighborhood level. To supplement facilities provided by junior
and senior high schools and provide close at hand recreational space.
Size: 10 to 20 acres
Acres/People: 2.5 acres/1000 people
36
Service Area: 2 to 3 oieighborhoods, 1 to 1.5 mile radius
Location: Should be central to the neighborhoods to be served and
have direct access to major transportation thoroughfares and bike
paths.
Facilities/Activities: Should be individually designed and shall
r. _
provide ball fields, tennis couris, multi-usp ems tu�pav ' eas..et>vall,
volleyball), picnic areas and cooking tacilities, open play a.
trails, restrooms, irrigation, trash receptacles, fencing, lighting,
off-street parking, and an internal road system to allow for police
surveillance. Should provide shelters, natural areas, and activity
centers. Facilities available through adjacent schools will be
included as part of the site requirements.
4. LARGE URBAN PARK.
Purpose: To provide the residents of a greater community with an
opportunity to get away from the noise and congestion of the cit;
without traveling a great distance. To provide large areas for
diverse activities encompassing passive and intensive uses.
Size: 50 to 150 acres
Acres/People: 5 acres/1000 people
Service Area: 5 mile radius
Location: Should be easily accessible by auto or transit. Ideally
located with access for water activities. Local pedestrian/bike
access shall be provided.
w:_ .
.' Facilities/Activities: - A large urban park shall provide regulation
"3 ball fields, picnic areas and cooking facilities, large open play
areas, drinking fountains, restrooms, trails, trash receptacles,
� .; internal road system off-street parking, landscaped areas, and
irrigation. It should provide tennis courts, shelters, and natural
areas.
5. REGIONAL PARKS
Purpose: To provide urban residents with an opportunity to get ,away
from the noise and congestion of the city without having to travel
great distance. To provide a large natural state area.
Size: 500 to several thousand acres
Acres/People: 15 acres/1000 minimum people
Service Area: An area which may cross county boundaries
r�
Location: Dependent on available resources. Ideallyadjacent to a
lake or river.
w
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Facilities/Activities: Campgrounds, picnic and day use areas, natural
areas, trails, restrooms, and parking shall be provided.
Water-oriented activities should be provided. Extensive development
niay also be included (sports complex or coliseum).
h. GENERAL OPEN SPACE
'Preservation Oriented - Subcategories may be combined)
Purpose: To encourage access and use of areas of natural and scenic
beauty at a level that affords protection of the various amenities of
the area and provides a base for community identity.
k Size: Community-wide overall ; individual components variable as
appropriate.
Variable, generally intended to benefit the entire
Yopuiation Se;"vev, „a....,,.�,
community.
A. Scenic Pathways:
Purpose: To provide linear areas of natural and man-made beauty which
will interconnect other elements of the park system, schools, and
other public places. To provide for conservation of scenic and
natural areas, especially water courses and areas subject to
flooding. To provide buffer areas along thoroughfares or between
conflicting land uses. To give a feeling of general openness to the
community.
Facilities/Activities: Scenic ways shall provide trails or walkways
and trash receptacles. The land shall be retained primarily in its
natural condition along waterways and other areas of natural value.
In areas where development has occurred, landscaping and design
controls shall be applied. Additional landscaping should be provided
along these corridors. Rest areas should be provided.
1211:
Location: Bordering waterways and areas subject to flooding, along
transportation and utility corridors.
B. Landscaped Areas:
f.
Purpose: - To beautify areas not serving an actual park function but
F; that would add to an atmosphere of open space.
Facilities/Activities: Facilities should be limited to walkways and
sitting areas; trash receptacles should be
provided.
,a
Location: Along major transportation corridors and interchanges,
A commercial frontages, plazas, malls, and parking lots.
C. Natural Preserves:
Purpose: To preserve unique resources and to make natural values
=) available for public education and enjoyment through visual contact or
an on-site experience.
M
-38—
Facilities/A._tivities: Natural preserve facilities shall include
those to protect and euliance the site, such a protective fencing or
guardrails, elevated walks, trash receptacles, and landscaping.
® Compatible activities would include walking, viewing, and nature study.
Location: Dependent on available resources.
7. WAFER-ORIENTED SITES
Purpose: To encourage access to and use of waterways. Sites -.-.-,ay
exist as individuals or as o?rt of a mu?.ti-use park.
Facilities/Activities: Appropriate uccr would be swimming, boating,
and fishing. Fishing access shall include trails and trash
receptacles, if appropriate. Improvements shall include docks, rafts,
parking, and trash receptacles.
Location: Dependent on available resources.
8. SPECIAL USE AREAS
Purpose: To provide areas and facilities for activities usually
requiring special facilities (e.g. courts and play£ields). These
special facilities generally restrict other uses on the same site.
They can be supplied individually or in complexes incorporating two or
' more of the uses in this category and should be constructed at a park
site.
Facilities/Activities: Depends on opportunity being provided. For
complexes, restrooms, and trash receptacles shall be provided. For
playfields. ballfields, and golf courses, irrigation and trash
Facilities such as rifle ranges are
receptacles shall be provided.
not likely to be provided within the community; however, programs
should be provided to use facilities elsewhere. Parking shall be
provided. Bleachers and lighting should be provided when appropriate.
Size: Depends on facility being provided and whether it is a complex
or single facility. Courts and fields shall be regulation size for
intended use.
Service Area: Depends on activity and type of facility (e.g. complex
or single) and the type of park it is located in.
9. CULTURAL FACILITIES
Purpose: To provide a place in the community for formal or informal
public gathering that will allow for increased cultural enrichment.
Facilities/Activities: Cultural facilities may include plazas, malls,
small -parks, fountains, open-air/indoor theaters, and a library and
meeting hall complex. Trash receptacles and benches shall be
provided. For landscaped areas irrigation shall be provided. Larger
facilities shall provide off-street parking.
u
—39
Location: Depends on facility being provided. Falls and plazas
should be placed in the commercial core or well developed areas.
larger tacilities should be located away from congestion; a plaza can
be incorporated into a larger facility or cun,plex. Should serve the
entire coma=unity.
10. 1_,lL11'Ol:TC SITES
Purpose: To identify and preserve local historic sites and structures
for enjoyment and education of present and future generations.
Facilities/Activities: Historic sites shall be developed or
incorporated in a development in a way that preserves the integrity of
the site or structure. Interpretive signs and trash receptacles shall
be provided. Parking, trails, picnic facilities, and protective
fencing should be provided when feasible.
® Location: Dependent on available resources.
11. ACTIVITY CENTERS
Purpose: To provide indoor areas for gatherings of local residents or
special age groups of the city's population.
Facilities/Activities: Could be for a specific age group (e.g. senior
citizens or youths) or the entire community. Centers shall provide
meeting rooms, kitchen or concessions, lounge, work rooms, restrooms,
trash receptacles, off—street parking, and landscaped areas. Could be
supplied in conjunction with a cultural center.
Location: Should be easily accevsible to all groups intended to be
served by the facility. Shall be located with a direct assess by
auto, ;-zansit or pathway.
Greenway/Path System
In addition to park land, this plan incorporates the greenway concept as a
means of providing open space and protecting the natural drainage system. It
establishes the greenway as the hub of the open space system. The greenway
was -originally proposed lit the 19171 Community Plan, which established Fantao
Creek and its major tributaries as a source of linear opan space. It also
proposed that the greenway system serve as a route for pedestrian/bicycle
travel. In 1974 the City adopted the Pedestrian Bicycle Path Plan. The plan
specified which portions of the greenway should function as actual pathways.
The 1974 pian calls for paths along:
1. The entire length of Fanno Creek within the plan area, I
2. Summer Creek from Tiedeman to S.W. 13
3• The watercourse that flows from Bull Mountain through Jack Park to
Summer Creek, and
t
—40—
:
' 4, The watercourse that follows through the Genesis, Pathfinder area to
S.W. Walnut Street.
.�,,..a�s; also provide excellent opportunity for
The areas listed above, as pa�.•�
passive recreation aad pedestrian/mike travel. Ilec�lsel` t�3C4ciGiLi'ou will
g;
benefit all lncal residential properties, financing
development should come from all residents l prnpPrtias in the Tigard Urban
plan which the City will develop during 1983Planning Area. The master park 1 pathway system.
will address the financing aspects of the pedestrian/bicycle p Y Y
Greenway Acquisition and Develo ment
ty in the floodPl
be
Development with portions of proper
land re area a area ll
within the
required to dedicate, to the City, the
floodplain/greenway. If a portion of the ped the owner ayshall tebe
I is incorporated on the property, the property
n of the
as adopted,
Lequired, at the choice of t�hev`tvtystandardsh that will er Construct
traversep the property,
pedestrian/bicycle pathway /bicycle pathway
or place the construction costs into the City's pedastr�an.
system development account.
Park Land Acquisition and Development- Program
The acquisition and development of parks and recreational facilities are
the
funded by a System Development Charge which is assessed on each new i
residential unit. the charge is
essed may be acceptedat the e in of
lieuofissuance
of
the fee
building permit. Dedication o plan for ark
approthe standards set in ved
sites and is
provided that by Parke Board. (See SDC Ordinance the
e Appendix I)p
approved y
FINDINGS
e '_28.80 acres of City park land in Tigard and 37.90
o Currently, there ar
acres of dedicated greenway.
o There are adopted plans for eight of the nine City parks.
Io Although Scheckla Park has not been accepted by the Park Board, the land
was dedicated to the City for park Purposes.
O Due to recent cut-backs in revenues to the City, the City has
substantially limited its park maintenance program
o The City's Park System Development Charge is acquired through new
development and is used solely for park acquisition)
for d velopmenhroughther major
capital acquisition. Park maintenance is paid
general fund.
POLICIES
' 3.6.1 INDIVIDUAL PARK SITES, AS DEFINED BY THE PARKS AND OPEN SPACE
STANDARDS AND CLASSIFICATION SYSTEM SHALL BE DEVELOPED ACCORDING TO
p
THE FOLLOWING PRIORITIES:
-41
1 w y,
a. FACILITIES WITHIN A PARK WILI. BE ADJUSTED TO MEET THE NEEDS AND
DESIRES OF THE DI5TRICI RESIDENTS AND THE CHARACTERISTICS OF THE
SITE. PARK AND/OR RECREATIONAL FACILITIES IN GREATEST DEMAND AND
LEAST SUPPLY SHOULD RECEIVE 'THE HIGHEST DEVELOPMENT PRIORITIES.
b. PARKS SHOULD BE PLANNED TO INSURE MAXIMUM BENEFIT TO 'THE CREATES]'
NUMBER OF LOCAL RESIDENTS. FOR THIS REASON, ACQUISITION AND
DEVELOPMENT OF COMMUNITY LEVEL PARKS SHOULD BE GIVEN THE HIGHEST
PRIORITY.
C. DEVELOPMENT OF ADDITIONAL NEIGHBORHOOD PARKS WILL HAVE A LOWER
PRIORITY FOR PUBLIC FUNDING AND ARE ENCOURAGED TO BE PROVIDED BY
THE PRIVATE SECTOR WITHIN PLANNED UNIT DEVELOPMENT'S AND MAIN'T'AINED
BY HOMEOWNERS ASSOCIATIONS.
d. NEW MINI PARKS HAVE THE LOWEST DEVELOPMENT PRIORITY AND SHOULD BE
SUPPLIED AT THE DEVELOPER'S OR NEIGHBORHOOD'S EXPENSE AND
MAINTAINED BY A NEIGHBORHOOD ASSOCIATION CREATED AS PART OF THE
DEVELOPMENT PROCESS.
e. PROVISION OF REGIONAL PARK FACILITIES WILL ONLY BE CONSIDERED AS
AN INTERJURISDICTIONAL PROJECT; AND SHOULD HAVE A LOW PRIORITY
UNLESS UNUSUAL CIRCUMSTANCES ARISE.
f. ACCEPTANCE OF ANY LAND DEDICATED FOR PARK PURPOSES SHALL BE BASED
UPON ITS USEFULNESS AND ADAPTABILITY TO THE ADOPTED PARK AND OPEN
SPACE SYSTEM.
3.6.2 THE CITY SHALL COORDINATE WITH OTHER PUBLIC, PRIVATE ORGANIZATIONS AND
AFFECTED PRIVATE PROPERTY OWNERS IN ORDER TO FACILITATE THE
IMPLEMENTATION OF THE CITY'S ADOPTED PARK PLANS.
IMPLEMENTATION STRATEGIES
t 1. The City shall continue to seek revenue sources to facilitate in the
implementation of the adopted park plans. The adopted park plans are:
Fanno Creek Park, Cook Park, Woodard Park, Jack Park, Summerlake Park,
Englewood Park, Liberty Park, and Ye Old Windmill Park.
2. The City shall develop a "future park needs assessment" to determine the
r number of acres needed for future park uses. The current park standards
shall be used as a basis for this assessment. The future park need
i
assessment will specifically address community park needs.
3. As a precondition to development, the City's Community Development Code '
shall require the dedication of the greenway and park land, if not already
dedicated.
4. The City shall continue to implement the adopted pedestrian/bikepath
pathway plans.
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f,
i
HISTORICAL - C::;,TURAL RESOURCES
In considering the overall character of the community, it is important to look
to the past. As a community develops it should not discard its past for the
sake of the future.
Findings
o Historic features provide a link with the past and add character and
variety to the community design. Unfortunately, much of Tigard's heritage
has already been lost to unmanaged development with only a few distinct
structures remaini&ig.
o The design of developments within the community can be regarded from two
view points; the design of structures as they relate to site and function
(architectural design), and their relationship to the surrounding area
(community design). Both aspects are of equal importance.
o Good architectural design is necessary to provide visual variety and allow
for individual identity. At the same time, good community design provides
a sense of unity with other development while eliminating conflicting
appearances.
POLICIES
3.7.1 1HE CITY SHALL IDENTIFY AND PROMOTE THE PRESERVATION AND PROTECTION OF
HISTORICALLY AND CULTURALLY SIGNIFICANT STRUCTURE, SITE, OBJECTS AND
DISTRICTS WITHIN TIGARD.
4
IMPLEMENTATION STRATEGIES
1. To preserve the community's history, an index of historic sites shall
be developed and made available to the general public.. A program
shall be developed to acquire and/or restore a number of historic
structures identified as significant. The City should consider the
renovation of a historic structure as an historic museum or cultural
3. Center and uieetin.- hail such as Durhari Scluoul, Ye Old Windmill and
John Tigard Home.
f
3K
V
t.
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o�
APPENDIX
NATURAL VEATLTRES AND OPEN SPACE
Ji
15
rsl_
Appendix A
HYDROLOGY
The Tigard Urbain Pian Area lies entirely within the Tualatin River Watershed,
which drains most of Washington County from the headwaters of major
tributaries in the Coast Range east to the Willamette River. The Tualatin
River basin is roughly 40 miles long and 25 miles wide and has an area of 711
square miles. The central reach of the river traverses a relatively level
valley and therefore meanders over a broad floodplain. In this central
section the gradient of the river is very slight; from the mouth of Dairy
Creek (River Mile 44.8) to Interstate Highway 5 (R.M. 6.5), the slope is 0.2
foot per mile or slightly more than 2 inches per mile. During the low flow
pe-riod of summer-early fall the slow flow permits the water to become heated
to warm temperatures. On the other hand, the low gradient facilitates
overbank flooding during winter-early spring storms, as does the lower gorge
(from R.M. 6.5 to the mouth) with its natural rock reefs. Removal of some of
these reefs is being evaluated as a means of reducing flood levels immediately
upstream where the City of Tualatin now suffers periodic severe damage. The
sn:eam. serves as the southern border of the plat area froom River mile 11.15
(U.S. 99) to the railroad bridge at R.M. 9.3.
Fanno Creee, is the last major tributary of the Tualatin River prior to its
incision through the low Tualatin Mountains to the Willamette. The Fanno Creek
Basin has a drainage area of 34.2 square miles (see table), encompassing the
most rapidly urbanizing portion of the Portland Metropolitan. area. Its
drainage divide follows (in a clock-wise direction) the crests of LIttle Bull
Mountain/Bull Mountain (710 feet), Cooper Mountain (770 feet), and Sexton
Mountain, then crosses a flat lowland east of Beaverton (which separates Fanno
Creek from Beaverton Creek), continues northeasterly through the south Raleigh
Hills area to a high paint north of U.S. 26 (Sunset Highway) at Sylvan (1060
feet), and from there follows the ridge crest of Portland's West Hills from
r'.-A
� .,. Council Crest (1020 feet) south over low passes (450 feet) to Mt. Sylvania
(960 feet). Stream slope averages 8 feet per mile. Approximately 826 of the
Tigard Urban Plan Area lies within the Fanno Creek basin. The stream is in
the plan area from River Mile 1.0 to 6.6.
The volume of water carried by the Tualatin River varies greatly with the
seasons: 70% of ,the;total yearly flow is discharged during the four winter
months (December_- March), and December and January together account for 40%.
Summer flows are a correspondingly _low fraction of the winter flows. Fanno
Creek exhibits a similar periodicity.
52
Table I
RIVER FLOWS-TUALATIN RIVER AND FANNO CREEK
Mean
Annual 24-hr. Minimum Flow 24-hr. Maximum Flow
Flow Median 1 in 10 yr. Median 1 in 10 yr. Record
Tualatin R.. 960 Mg 36 23 7,130 11,280 19,000
Fanno Ck. 29 1 -- 340 -- --
Most of the upstream portions of the major Fanno Creek tributaries are outside
the plan area, as is also true of Fanno Creek itself. In order of decreasing
drainage basin size (also see Table II), the largest tributaries which flow
through the area are:
1. Summer Creek
2. Ball Creek
3. Ash Creek
4. Redrock Creek
5. Pathfinder Creek (?) - largest wholly within plan area
6. Hiteon Creek
Most of the watercourses in the plan area are without official names, a
situation whicit should be remedied to facilitate future reference to them. A
list of the purely local streams excluding Fanno Creek and the Tualatin River
would include the following, in generally clockwise direction from the
southwestern border of the plan area: (with suggested names)
Willowbrook (called Willowbrook Creek locally) which drains directly to
Tualatin River between 108th and 113th south of Durham Road. The
watershed includes south slope of .Little Bull Mountain (W. of 98th), King
City, and S.E. slope of Bull Mountain (east from 133rd), S. of`Durham Road
W. from 100th. Three forks S. of Durham Road are still in relatively
natural condition. The W. fork has been filled (King City and Royal
Mobile Village).
Small unnamed watercourse (Durham Creek?) - Drains to Tualatin River south
of Durham Road in the vicinity of. 98th.
A few short (1/2 mile) drainage swales & interm_.ittent watercourses which
drain east to Fanno Creek between Bonita Road the Durham Road.
Pinebrook Which flocs north from Sattler, then crosses Hall Boulevard to
Fanno Creek north of Bonita.
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Unnamed (McDonald Creek) - Deep drainage swale flows east along south side
of McDonald Street, then crosses and heads northeast to Fanno Creek east
' of Hall.
i Unnamed (Frewing Creek) - Drainageway flows north from McDonald Street to
Fanno Creek, paralleling Pacific Highway (to the west).
Unnamed (Pathfinder Creek) - Two forks drain northeastern, moderately
steep shoulder of Bull Mountain (125th) and area immediately to the West
of Pacific Highway. This is the largest stream almost wholly within the
plan area, and once also drained the northwest slope of Little Bull
Mountain. Flows northeasterly into Fanno Creek. Some storm discharge
calculations have been made by consulting engineers for private developers.
Unnamed (Fonner Creek) - Last (easternmost) tributary of Summer Creek
drains small basin on lower slope of Bull Mountain southwest of Marion and
121st, flowing in northeasterly direction.
Unnamed (Walnut Creek) - Fairly large tributary of Summer Creek drains
northeastern heights of Bull Mountain through very steep, heavily wooded t
canyons. Two separate forks each drain large areas (western fork also �
apparently bifurcates at just below the upper steep slopes), converging in t
a sizable floodplain just above Summer Creek. Chamberlain Lake is an f
impoundment in the east fork while Jack Park is located along the west
fork.
Unnamed (Bellwood Creek) - Short, narrow watercourse flows north to Summer
Creek (West Summer Lake) from Walnut Street at 132nd.
Unnamed (Sunamoto Creek) - Small watercourse east of 135th drains a
middle-altitude ridge of Bull Mountain. Flows North into a large pond
before entering floodplain of Summer Creek (West Summer LaKe). A smaller
drainageway converges from the west below the pond.
f
Summer Creek The largest tributary of Fanno Creek drains the northern
slopes of Bull Mountain, the southeastern and eastern slopes of Cooper
Mountain, and the south slope of Sexton Mountain, flowing east to Fanno
Creek. The drainage basin is roughly 3.5 miles long and 2 miles wide with
a total area of 5 sq. mi. The entire portion within the plp,% area has a P
low gradient and consequent floodplain. Two impoundments are sizable
lakes (West and east Summer Lakes) formed by a small check-dam. The great
proportion of the watershed is still undeveloped, consisting mainly ,of
farms and woodland. It is the sole remaining major tributary of Fanno
Creek in that condition (Ball Creek -- the only contender -- is going to
be rapidly urbanizing over the next several years), and therefore has the
best water quality as well. C
E
Hiteon Creek) - A fairly long but narrow tributary of Fanno, Creek flows
southeasterly off the east slope of Sexton Mountain and traverses the
Englewood subdivision. The portion in the plan area is a low-gradient
floodplain, with a pond near the confluence with Fanno Creek.
Ash Creek - This is the second largest tributary of Fanno Creek. It flows
southwesterly from its origins on the northwestern shoulder of Mt.
Sylvania and gh areas to the north. Its basin is about 3 miles long and
1.5 miles wide (over 4 sq. mi.). Its southern drainage includes Metzger i
-55-
and south Garden Home. The portion in the plan area is a low gradient
floodplain with a small drainageway entering from he east. The basin is
largely urbanized and therefore water quality is rather poor and flooding
co►ttinou during storms.
Redrock Creek - This fourth largest tributary of Fanno Creek drains
southwesterly from the northwest heights of Mt. Sylvania where the
drainage divide with Ball Creek on the south is rather indeterminate. The
lower portion of the stream is a low-gradient floodplain. Few hydrologic
measurements have been made on the stream.
Ball Creek - This third largest tributary of Fanno Creek drains the
southwest slopes of Mt. Sylvania, flowing southwesterly to its mouth. The
short lower section within the plan area has been extensively channelized,
but east of Interstate 5, 90% of the basin is in woodland or agriculture
with only 5% impervious surface. Little hydrologic data is available.
Relatively little reliable hydrologic information is available on local
streams, even for Fanno Creek. This may be remedied over the next few years,
at least for the largest ones, as some major research projects are completed. C
In a few months, the U.S. Army Corps of Engineers will be finishing a E'
floodplain study involving Fanno Creek, Summer Creek and Ash Creek. City
efforts to have Redrock Creek including in this study were unsuccessful. A
regional investigation into rainfall-runoff relationships and the effects of
other variables such as basin size, slope, urbanization is now underway by the
Corps and U.S. Geological Survey. When it is completed in several years, much [
more accurate description of local hydrological conditions will be possible.
Meanwhile, the Tigard area will be the subject of the drainage study by the ;
City of Tigard in fiscal year 1977-1978. At the present time, however, there
is apparently more data on water quality (pollution) than water quantity.
Urbanization of the Tigard area creates several water resource management ;
problems includii.g flooding, water pollution, and declining ground water
levels. With regard to flooding (also see following appendix), the Tigard
area is the recipient of the exportation of drainage/runoff of upstream
urbanization, especially from Multnomah County, Portland, Metzger, Garden Home
and Beaverton. The steep slopes of the West Hills have sluiced more storm
water downhill as they KL%re been covered with impervious surfaces. Flood
storage areas within the floodplain have also been filled and developed,
causing higher flood crests. For any given storm intensity (precipitation per
hour), flood crests/frequencies in he Fanno Creek basin can be expected to
continue to rise as urbanization proceeds. The major contributors will be
F
floodplain filling (unless severely restricted), further development in the
West Hills of Portland, and new development of Mt. Sylvania, Bull Mountain and
Cooper Mountain. The steep slopes and drainageways of the latter areas will
require stringent protection if there is to be any hope for a leveling off of f
increasing flood problems. Since this is the basinwide problem, enactment of
protective measures within the plan area must be matched by effective
watershed management by upstream jurisdictions.
The Tigard Plan Area has 16 large ponds and lakes. They range in size from
over 4.5 acres to about one tenth acre (see Table II).
j ;
i '
i
LT
-56-
i
Table III
LAKES AND PONDS-TIGARD DETAILED PLAN Ai.EA
In Order of Size
(Suggested Names)
West Summer Lake (also see East Summer Lake) - east of 130th and south of
Scholls Ferry Road.
4.76 acres
Chamberlain Lake - north of Walnut at 123rd
2.33 acres
East Summer Lake (also see W. Summer Lake) - west of Summercrest Drive south
of Scholls Ferry road
2.20 acres
(Sunamoto Pond) - west of 130th south of Scholls Ferry Road
1.75 acres
(Hiteon Lake) -south of Ironwood Loop near Fanno Creek
7,60 acres
Crystal Lake - south of Pacific Highway between Highway 217 and Garden Place
0.85 acres
r.r
(Lower Pinebrook Pond) - also see Upper Pinebrook Pone) west of Hall south of
Pinebrook
0.40 acres
(Walnut Creek Pond) between Walnut and Alberta
0.39 acres
(Fonner Creek Pond) - near Fonner east of Carmen
t
Lower Omara Pond) - also see Upper Omara Pond) - north of Omara
0.39 acres
(Bedrock Pond) - east of Highway 217 and northwest of Hermanso
0.38 acres
(Upper Pinebrook Pond) - see also Lower Pinebrook Pond) - west of Hall south
of Pinebrook
0.38 acres
(Fanno Creek Pond) - also see Fanno Creek Pond, Lower) - east of Hall and Omara
0.31 acres
(Sattler Pond) - south of Sattler west of Hall
0.27 acres
(Upper Omara Pond) - also see Lower Omara Pond) •- north of Omara .
0.15 acres
(Fanno Creek Pond, Lower) east of Hall and Omara
n-11-acres
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1
++i
i
Appendix B
FLOODPLAINS AND WETLANDS
L
Although occasional flooding of streams in the Tigard area occurred under
natural conditions, mainly in the winter, urbanization has led to more
frequent auent f
loods, especially
along Fanno Creek and its tributaries (see text
for fuller explanation and diagram). The streams subject to major flooding G
all have low gradients and include:
i
i
Tualatin River
Fanno Creek
Summer Creek
Ash Creek
Redrock Creek
Flood discharge estimates have been made for the three largest Tualatin
tributaries in the Tigard area (see Table IV). `
In the past, most of the difficulties have involved Fanno Creek and the
Tualatin River, for which the U.S. Army Corps of Engineers has a fragmentary
flood damage record extending back more than 40 years. The following record
is for the Tigard Detailed Plan Area:
Flood Location Type of Damage Amount of Damage
1933 Fanno Ck. Agricultural $2,280
Other 540
Total 2,820
1949
1955 Agricultural Total 900
Agricultural 700
Residential 7,160
Commercial-Industrial 2,000
Total 9,860
196465 Tualatin R. Residential 6,200
Agricultural 8,650
Commercial-Industrial 36,200
Fanno Creek Residential 200
Agricultural 2,840
t Total $54,090
1974 Tualatin R. Roads 210,000
Fanno Creek
1977 Fanno Creek Residential, NA
Total $264.090
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tF
Table IV
FLOOD DISCHARGES WITHIN THE PLAN AREA (FANNO CK. , ASH CK. , SUMMER CK.)
i
s
Preliminary A7ood _rischArges-Jan 77 �
_ �
Drainage Recurrence Interval Discharges, cfs
Location Description Area
Sq. Mi. 10-Year 50-Year 100-Year 500-Year
I'
FANNO CREEK
Mouth of Fanno Creek 34.2 1330 2200 2600 3700
S.W. 85th 30.5 1250 2000 2400 3400
18.5 850 1360 1620 2250
Downstream of Summer Ck.
SW North Dakota 17.4 810 1300 1550 2150
13.3 750 1200 1380 1940
Upstream of Ash Creek
ASH CREEK
Mouth of Ash Creek 4.13 137 417 534' 848
At SW Oak 3.00 130 320 420 670 r
}
SUMMER CREEK -
Mouth of Summer Creek
5.04 799 1098 1210 1530
SW 116th 4.83 758 1065 1198 1510
SW 135th, 2.93 515 723 809 1034
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The largest recent flood event was in January, 1.974. Overall flood damages
for the general Tigard area were roughly estimated by Washington County and
the Carps at between t40,000 and $150,000. Damage to City of Tigard property
alone was estimated by the City Administrator at $210,000 (mostly roads).
City of Tigard employees helped protect the City of Tualatin by working
through the night - at a cost of about $1,000.
During the 1974 flood, water flowed over 5 bridges crossing Fanno Creed:,
forcing temporary closure of these roads within the plan area:
North Dakota
Hall Boulevard
Tigard
Grant (water was measured 42" over the bridge but this is not
consistent with the following Corps table and the fact
that Main Street was above the water).
Scholls Ferry Road
In the December, 1977 flood, all of these bridges except Scholls Ferry were
closed. The Main Street bridge over Fanno Creek was threatened during that
flood, and another foot or two of water could conceivably have collapsed the
structure, a possibility that worried General Telephone: The steel ducts near
the bridge carry communication lines to King City, Sherwood and Newberg.
During the 1974 flood, a family was evacuated from the flooded house on Grant
Avenue and a city employee was evacuated from Cook Park. The ground floor of
the Lu Jon Park Apartments was also flooded at that time.
During the more recent but smaller flood of December, 1977, the tributaries of
Fanno Creek also had high water. Ash Creek was within 8 inchpc of the to of
the Oak Street bridge, and all four corners at the intersection of Oak and
Hall were under water. A drainageway into Ash Creek (from the area north of
Pacific Highway) was over its banks west of Hall: all of the houses on the
south side of Thorn Street were surrounded by water and 89th was entirely
under water from its intersection with Thorn to its southern terminus.
Redrock Creek flooded 72nd (blocked culvert) and was over the road at
Hunziker, which had been designed to allow this. Ball Creek overflowed Bonita
Road due, apparently, to inadequate culvert size. Water was reported over
several other roads in Tigard, including Hall (south of McDonald), Frewing,
121st (north of Albert), Walnut (near 124th), Burnham (both east and west
ends), and Tigard (at Grant). Lack of culverts, undersized culverts, and
general lack of a drainage system were responsible for these incidents.
As a consequence of the 1974 flood, the City of Tigard enacted a floodplain
ordinance one year later. The ordinance restricts activities within the.
100-year floodplain (area having at least a 1% probability of being flooded in
any year) and requires special permits for fills or structures. Washington
County also has a similar floodplain ordinance. Since that time„the"City has
Erected-a Zero-Foot Floodplain Ordinance,which further restricts development
within the floodplain area.
City and County restrictions on land use in the floodplain make property
owners eligible to participate in the National Flood Insurance Program. This
program makes floodinsurance available to interested persons at modest cost.
individuals should contact the Tigard Planning Department ,for additional
information.
c -60-
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i
The floodplain ordinance, as originally adopted, referenced relatively s
inaccurate maps as officially delimiting the floodplain. These air photo maps
are at scale 1" = 1000' whereas the City has more precisely mapped the
floodplain on topography maps at scale 1" = 100'. These more exact City
floodplain maps are based on the 1979 Corps study and calculations of the r
100-year flood crest for Fanno Creek and the Tualatin River at several
bridges. Interpolated water surface profiles permitted the delimitation of
fairly precise floodplain lines along the two main streams. The City
floodplain maps are now the ones recognized by the National Flood Insurance
Administration.
i
The Corps study was not as detailed for the troublesome tributaries of Fanno
Creek. On a small-scale map it showed the 100-year floodplain of lower Ash
Creek as far as Highway 217 and the lower one-quarter mile of Summer Creek.
The Washington County Public Works Department then compiled small scale
airphoto maps of the floodplain for the major maps with 10' contour intervals
as the data base. These maps were the ones cited in the City's original
floodplain ordinance. The larger scale (1" - 1001) City floodplain maps, with
2' contour intervals, generally follow the county maps on the major
tributaries. On Redrock Creek, the floodplain is based on unpublished Corps
data. City floodplain maps for Summer Creek deviate slightly from the county
map on the basis of flood information contained in Zone Change file 2-75 (Iron
Mt. Investment Co.). The Ash Creek floodplain east of Highway 217 has been
estimated by City staff.
The Corps of Engineers is currently conducting a much more detailed floodplain
survey on Fanno Creek, Summer Creek, and Ash Creek. The results of this
survey may require Further revisions in the official floodplain maps in about
one year.. The USGS - Army Corps rainfall/runoff study may provide enough date
to permit final revisions to account for urbanization effects when it is
t
completed in several years. `
During a 100-year flood, almo;;t 600 acres of land would be under water along
the major streams (see Table V). A total of 31 homes, housing about 93
people, and 6 business structures are in the floodplain (see Table V). More
than two-thirds of these houses are located at two locations: along Summer
Creek between 121st and 116th (13) and on Fanno Creek in the vicinity of
Johnson Court (8). Many of the bridges on local collectors and arterials
would be under water in a 100-year flood (Tables VI and VII).
Wetlands and Poorly Drained Areas
Areas which are poorly drained or have seasonal standing water or high water
tables can also pose special difficulties. For purposes of this study,
wetlands and poorly drained areas were defined to includes:
Poorly drained soil (SCS-seasonal water table within 1 1/2' of surface)
Watercourses and drainage swales }
Enclosed depressions
The 1977 storm dramatized Tigard's growing storm drainage problems. They are
especially acute in 'NPO #2 on Lincoln and Commercial and on Tigard Street
between Grantand Tiedeman. Ponding also occurs along Burnham during heavy
rains. (Storm drains will be installed on Burnham and Tigard in he spring of
1978). The basement of a house on 107th and Park has also been filledwith
61
i
water after heavy rains. Drainage problems will become magnified as the area
is more completely urbanized unless action is taken to forestall future
difficulties through development of a storm drainage system. A highly
promising approach is the one adopted by the City of Bellevue, Washington,
which is based on retention of natural drainage-ways and fees calculated on
the amount of runoff generated by the development of a site. A consulting
engineering firm is now conducting a comprehensive storm drainage study of the
Tigard area.
-62-
_..
Table V .;
• STRUCTURES IN 100-YEAR FLOODPLAIN (NC-NON-CITY)
Tigard Urban Plans Area
i
e
Summer Creek - 130th Street, - unimproved (unpaved) road
125th - earthen dam
between 116th - 121st - 13 houses
121st road - roadbed
S. end of 113th - outbuilding
Fanno Creek - Scholls Ferry Road - roadbed (NC)
S. of Ironwood Loop - earthen dam on Hiteon Creek (NC)
N. of N. Dakota - abandoned sewage treatment plant (NC)
W. of R.R. at Cascade - 1 house and 2 outbuildings (NC)
Ash Creek - Spruce Street - 1 house (NC)
Thorn and 88th - i house (NC)
95th off Oak - 1 house (NC)
95th off Oak - roadbed (NC)
off Greenburg - 2 outbuildings (NC)
Cascade Bouievary - 2 business structures (NC)
Greenburg Road - bridge and roadbed (NC)
Fanno Creek - N. Dakota Street - bridge and roadbed (NC)
Tigard Street - bridge & roadbed (1/2 NC)
N. of Tiedeman bridge 2 houses
Tiedeman Avenue - bridge
S. of Tiedeman bridge - 1 house (?)
E. of Tiedeman - swimming pool
Clydesdale Place - 1 house
Johnson Street (W.) 1 house
Johnson Court - 6 houses
Woodard Park - footbridge
off Katherine Street - outbuilding
off Johnson Street - outbuilding
off Johnson Street - outbuilding
Grant Avenue - bridge and roadbed
between Pacific & Main - business structures
Main Street bridge
off Ash - settling ponds of abandoned sewaga plant
Ash Avenue - business structure
Hall Boulevard - bridge & roadbed
S. of Hall bridge - outbuilding (?)
Redrock Creek Hunnziker - 2 business structures
Fanno Creek N. of Bonita Road church and outbuilding
-, Bonita Road - bridge and roadbed
6
Tualatin River - off Pacific 1 house and swimming pool (NC)
108th Avenue 1 house
Cook Park - I house (NC)
3 other ,buildings
-64-
12/77
i
SummaiY
f
iiousea 31 (25 in City)
Population ("house) - 93 (75 in City).
Business Structures - 6 (4 in City)
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* Other structures - 35 (22 in CitY)
* Assume bridge and roadbed 1 structure
i
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Table VIII
FLOOD ELEVATIONS AT BRIDGES ACROSS THE TUALATIN RIVER
100•-year Underclearance
Mile flood Above Below
above Floor crest 100-year 100-year
mouth Identification elev. elev. Elev. flood flood
feet feet feet feet feet r
8.3 Interstate 5 133.5 124.1 126.0 1.9 -
8.6 Boones Ferry Road 134.3 124.5 129.0 4.5 -
11.5 U.S. Highway 99W 142.3 128.0 135.3 7.3 -
11.5 U.S. Highway 99W 143.8 128.0 125.6 - 2.4
j,
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Appendix C
GEOLOGY
Geologic Structure
Tigard lies within the Tualatin Basin, which is a shallow-snycline divided in
part by the central anticlinal Cooper Mountain ridge. This area therefore
straddles the southeast portion of the central anticline, a complex,
moderately steep synclinal trough to he north, and the lower slopes of the "~
Tualatin Mountains (Portland Hills, West Hills). The Tualatin Mountains
consist of separate linear folds, with the Troutdale Formation and Boring Lava t
softening the surface topography through partial filling of some of the
synclines. Linear depressions which partly surround the Bull Mountain
Cooper Mountain Ridge are apparently steep folds or stepped fault
displacements, and the two small uplands are separated by a similar feature
which probably marks the location of a fault.
f
Tectonic Activity (Earthquakes)
Oregon is located within one of the most tectonically unstable regions of the j
earth, where volcanic activity and earthquakes are manifestations of
geophysical processes occuring many miles below the surface over cress the °
size of subcontinents. The Portland area, therefore, has a continuing history
of major seismic events. Tigard itself was the epicenter of a 1941 earthquake
with an intensity of IV (see Table VIII for information on associated human i
impact). Large quakes in Puget Sound also impact this area, the 1965 event
which cracked the capitol dome in Olympia, for instance. A 1972 statistical
study of previous local quakes forecasts a 100-year event (1% probability per
year) of intensity almost X. A 1974 estimate, however, used a different
technique, and a quake of intensity VII - VIII is predicted for a 100-year
event.
Although no direct surface evidence of faults occurs in Tigard, an analysis of
well logs suggests that two relatively inactive faults may exist. The depth
to the surface of the Columbia River Basalt beneath the valley floor appears
to;be displaced along two lines.
1. Between Cooper Mountain-Bull Mountain and along a line trending toward
the northeast.
2. From the southwest corner of the plan area at the Tualatin River
northeasterly to the vicinity of the junction of I-5 with Pacific
Highway.
Further discussion of the potential earthquake hazard is found in the text.
Geologic Units
The geologic formations which outcrop in the Plan Area lie on top of
sedimentary rocks of largely marine origin, dating from Oligocene (36-25
' million years) and possibly Miocene (25-13 million years) age. During the
Miocene epoch, more than 13 million years ago, a series of lava flows, known
as Columbia River Basalt, completely blanketed this 'earlier deposit.
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Table IX
SCALE OF EARTHQUAKE INTENSITIES WITH APPROXIMATELY
CORRESPONDING MAGNITUDES
Maximum Magnitude corre-
Intensity Description of effects accerleration sponding to highest
characteristic effects of the ground intensity reached
I Instrumental: detected only be seismograph 10
3.5
II Feeble: noticed only by sensitive people 25
to
III Sight: like the vibration due to a passing lorry;
felt by people at rest, especially on upper 4.5
floors 50
IV Moderate: felt by people while walking; rocking
of loose objects, including standing vehicles 100 4.3
V Rather Strong: felt generally; most sleepers are to
wakened and bells ring 250
4.8
V7 Strong: trees sway and all suspended objects swing;
damage by overturning and falling of loose 4.9-5.4
objects 500
VII Very Strong: general alarm; walls crack; plaster 5.5-6.1
falls 1,000
VIII Destructive: car drivers seriously disturbed;
masonry fissured; chimneys fall; poorly con- 6.2
strutted buildings damaged 2,500
to
IX Ruinous: some houses collapse where ground begins
to crack, and pipes break open 5,000 6.9
X Disastrous: ground cracks badly; many buildings des-
troyed and railway lines bent; landslides on 7-7.3
steep slopes 7,5000
XI Very Disastrous: few buildings remain standing;
bridges destroyed; all services (railways, 7.4-8.1
pipes and cable) out of action; great land-
slides and floods 9,800
XXI Catastrophic: total destruction; objects thrown 8.1
into air; ground rises and falls in waves (maximum
known, 8.9)
w„
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Columiba River Basalt
This formation underlies the entire area, but ouLerops only on Bull Mountain
and Little Bull Mountain. It consists of numerous well-layered lava flows
(30-6Q feet) with relatively little sediment between them, aggregating many
hundreds of feet thick (1,000 feet thick under Cooper Mountain). The
unweathered rock is blocky, jointed, and dense, varying in color from brown to
black or dark gray.
The surface of the Columbia River Basalt is deeply weathered in most of the
upland areas and lowlands. The top 20-200 feet has decomposed in places to a
red or brown clayey soil containing large quantities of oxides of iron and
aluminum and known as laterite.
i
Together with the younger Boring Lava, this unit is the only consolidated rock
which appears at the surface in the Tigard area (West side of Little Bull
Mountain at Pacific Highway). Although it is generally an excellent
foundation material, numerous factors such as degree of weathering, jointing,
thickness, adjacent formations, slope, etc. all must be considered on specific
sites. A massive landslide in this formation near West Linn suggests
potential problems caused by interflow sediments when saturated. The
weathering of the surface makes the basalt rather impermeable (see Ground
Water Appendix).
Troutdale Formation
An elderly Pliocene lake apparently deposited the semi-consolidated silt, clay
and sand overlying the Columbia Basin Basalt in the northeast corner of the
Tigard area. This unit may also extend farther west under the Willamette
Silt. Thickness is probably in the range of 100-300 feet.
There is a ralative dearth of information on the engineering characteristics
of this formation, but they appear to vary considerably, depending upon site.
Soil tests and engineering analysis would appear appropriate for major
construction activity.
Boring Lava
Portions of the Troutdale Formation are covered by Boring Lava, w;:ich occurs
from the northeastern border of the plan area as far south as the Rolling
Hills subdivision. There has been relatively little erosion of this geologic
j unit since it is rather young, dating from late Pliocene to possibly late
Pliestocene times, i.e. 5 million years to less than l million years ago. Mt.'
Sylvania was apparently the volcano from which this lava was extruded over an
eroded surface. The downslope edges of the flows are covered by 30-50 feet of
Willamette Silt. A conspicuous outcropping occurs on the north side of
Pacific Highway.
Although the lava can vary in thickness from a few feet to 300 feet, local
drilling indicates a depth of at least 50 feet. It is a massive, bluish-gray
basalt with blocky jointing usually widely spaced. Except where excavations
have exposed it, the unit is generally covered with as much as 20 feet of soil
or more. Weathering has occurred as deep as 46 feet, below the surface of the
basalt, leaving large residual boulders and a red clayey soil similar to that
produced on Columbia River Basalt.
-70-
1 mi'e noring t t_ like Columbia Rive Basalt for engineering purpose
illC Ll/L llljj 46 Vt1 1S Wl3 C:ll 1110. u ��.r � �`•b a•"-`�' purposes:
while generally providing good foundations and few limitations, specific site
characteristics may require a different assessment. Where heavily weathered,
the residual clay soil is impermeable. Large boulders may pose special
excavation and disposal problems. Excavation is unweathered rock may require
explosives. Finally, the possible occurrence of lava tubes, as discovered at
the site of the new St. Vincent Hospital, can be responsible for considerable
extra expenses when large structures are involved.
Helvetia Formation
This formation, of about the same age as the Troutdale Foration, consists of
unconsolidated reddish-brown and light-brown clayey silt and sandy silt
deposited on the surface of Columbia River Basalt to a depth of 15-145 feet.
It occurs along the mid slopes of Bull Mountain-Little Bull Mountain. Where
heavily weathered, it is converted into a lateritic soil difficult to
distinguish from soils derived from local basalts.
Where undistributed, the unit can support light structures, but saturatuon or
disturbance pose difficulties since either causes disintegration into
constituent particles. Vertical road cuts will stand where slope cuts will be
eroded by gullies. in addition to low permeability, the Helvetia Formation
has low to moderate compressibility and shear strength.
Upland Silt
The origin of Upland Silt is in dispute, but its basic characteristics are
not. It is a massive, structureless yellow-brown to buff sandy silt and
clayey silt. It was deposited (1-55 feet in thickness) over the Helvetia
Formation and Columbia River Basalt and therefore occupies the top of Bull
Mountain-Little Bull Mountain. In age, the Upland Silt probably dates from
middle to late Pleistocene times and so may be partly equivalent to the
earliest Willamette Silt. Indeed, some of it may derive from aeolian
transport of this material (loess). .
Although stable when dry, Upland Silt is unconsolidated and is unstable when
moist. It also has low permeability. Some settling is to be expected even
for light loads supported by spread footings, and heavy loadings cannot be f
supported. A high moisture content seriously weakens earth slopes and heavily }
stressed foundations. Mud flows and slumps are often observed on surface
slopes of 15% or more. Instability is also to be expected where the Upland
Silt rests on basalt which slopes with the surface contour.
f.
Willamette Silt
Unconsolidated sand, silt and clay mantles nearly all of the area below 250
feet elevation to a depty of 20-50 feet below the surface. The origin of the
deposits may have been several dozen large Columbia River floods during the k
Pleistocene. Carbon-14 dating suggests a period between 35,006 and 19,000
years ago. The formation consists of stratified beds from several inches to a
few feet thick. Clays are locally concentrated in poorly drained areas or at
a shallow depth below the surface.
The Willamette Silt is relatively weak and moderately compressible. Heavy
loads cannot be supported by the formation, and settlement is to be expected E -
for light to moderate loads. Moisture content and proportion of clay are
factors which contribute to the engineering difficulties o this geologic unit.
-71-
Lacustrine Sand and Gravel
The i�t~soula Flood of late Pleistocene times apparently occurred during the
period of deposition of the Willamette Silt, perhaps as recently as 15,v^OO
years ago (see text on p. 11). The torrential floodwaters left two distinct
deposits in the Tigard Plan Area: a gravel deposit in the southeast near
Durham and a belt of sand stretching south of Durham Road from 42nd west past
Pacific Highway.
After plunging through the narrow Oswego gap, the water quickly slowed and the
heavier materials fell out. Coarse—bedded bouldery pebble and cobble gravel
is found in a matrix of silt and medium to coarse sand at the Durham gravel
pit. The boulders are a large as 5 feet in diameter. large globular masses
of clayey material several feet in diameter were apparently rolled short
distances. Quartzite and granite cobbles were transported from southeast
Portland and limonite cobbles from Lake Oswego. The Durham deposit is over 75
feet thick.
The lighter sand was deposited immediately "downstream" in cross beds at least
50 feet thick (at Onion Flat on the south side of the Tualatin River). They
are medium to coarse—grained sands with thin pebbly lenses.
These sands and gravels are valuable mainly as sources of a,gregate and borrow
materials. The gravel mined at Durham is used for road construction while the
sand can be used for high—quality fill materials. The gravels will support
heavy loads with only minor settling.
f Glacial Erratics
The Missoula Flood carriedglacial icy which contained fragments of geologic
®. deposits from the Rocky Mountains. Melting of the ice left these materials of
foreign origin erratics scattered throughout the Willamette Valley,
including the Tigard area. —Numerous erratics have been unearthed {.n the
Durham gravel pit, and some are quite large — several feet in diameter.
Several sizable erratics were also identified elsewhere in the area more than
40 years ago, in Sectica 36 (northeast part of Tigard) and on Little Bull
Mountain in Section 10, but it is not known whether they still remain there.
Young Alluvium
The-floodplains of major streams — Tualatin River, Fanno Creek, Summer Creek,
Redroek-Creek, Ash Creek, etc., contain a surface alluvium deposited since the
close of the Pleistocene Ice Age. In composition this material consists of
silty clay, clayey silt, find sand, organic clay, and peat. The deposits are
20-30 feet deep and are frequently characterized by a water table at or near
the surface for much of the year.
The silt phase is weak and moderately compressible; the clay is very weak and
highly compressible. Only the lightest structures tolerant of some settlement
can be supported by the clays, and the silt will not support heavy loads or
light loads intolerant of some settlement.
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Appendix D
GROUNDWATER
Beneath the surface of the ground, at depths paralleling surface topography in
a very muted way, lies a zone saturated with water: the surface of this zone
is the called water table. The level of the water table depends upon recharge
from precipitation which gradually infiltrates down through soil and rock, and
discharge where the ground surface is below the zone of saturation (e.g.
springs). Human withdrawal of groundwater can also lower the level of the
water table, but otherwise this level is dependent upon the seasonal and
longer-term distribution of precipitation. Groundwater serves as a natural
reservoir for much of the water entering surface streams, so that during the
low precipitation season there flow may consist substantially of ground-water
discharge. Where underground layers of impermeable material occur at levels
above the regional water table, a small zone of saturation is created by
infiltrating water: this is called "perched" ground water.
In the Tigard area the water table is at about 200 feet altitude below Bull
Mountain and descends toward the level of the surface streams on the valley
floor (e.g. Summer Creek). However, perched water within a few feet of the
land surface is common over most of the area because of the soils (see
appendix on soils) and geological deposits (see Geology Appendix). The soils
tend to have concentrat*ons of fine-grained materials (clay), which not only
causes a great deal of precipitation of runoff as overland flow, but also
impedes vertical movement of water which does infiltrate. the geological
deposits underlying the soil are also often poorly permeable. The surface of
Columbia River Basalt, for instance, weathers to a clay, and the individual
lava flows -re very dense. Ironically, this formation also is the major
groundwater aquifer.
Each of the geological deposits have characteristics which distinguish them as
water-bearing strata:
Upland Silt is a thin unit above the regional water table.
Helvetia Formation is generally thin and usually lies above the regional water
table.
Boring Lava generally lies above the water table and has little permeable
material in its rew small interflow zones. Perched water occurs in limited
quantities,
Troutdale Formation is composed of interstratified sediments and contains
significant quantities of groundwaLer.
Willamette Silt consists of sedimentary deposits several hundred feet deep,
saturated a ew dozen feet below the ground surface. They are not very porous
because of the high clay content, however, and therefore have only low yields
(2.5 - 40 gallons per minute) sufficient for domestic wells.
Columbia River Basalt generally occurs in the saturated zone under the other
Mountain-Little Bull Mountain). Vertical
deposits (except on Bull
permeability between the lava flows is very poor but the interflow zones
contain porous material permitting relatively free movement of water. In
-73-
contrast to the water found in the Willamette Silt, some of the water in this
deeper unit is confined, so that wells tapping it have water levels near the
ground surface. Wells in this deposit yield enough for large scale use
(10-1,089 gallons per minute), making it the most important ground-water
aci>>+fer in the area.
The seasonal water table varies significantly with precipitation, reaching the
lowest point in September o: October and then rising to a high point in late
December or early January, rejecting subsequent winter precipitation as
surface runoff. The annual fluctuation averages 15 to 20 feet. Recharge
during late fall-early winter is equivalent to about 11 inches of
precipitation.
In 1973, a Critical ground Water Area was declared on Cooper Mountain and Bull
Mountain, including about half of the Tigard Urban Plan Area (west of Hall and
southwest of a line from Hall at McDonald to Scholls Ferry at 121st). Between
1960 and 1970, water levels declined 70 to 80 feet in the Tigard well field.
In the latter year no new applications for ground water permits were accepted
by the state engineer within the proposed critical area. Between 1970 and
1973, it is estimated that ground water withdrawals averaged about 6,000 acre
feet per year, of which about one-fourth was from the four Tigard Water
District wells. Preliminary estimates show that recharge is only 2,900 acre
feet, or 48% of this figure. The difference-- 3,100 acre feet -- was the
amount removed from storage and therefore responsible for the falling water
levels. A continuing decline in water levels in the basalt quifers might
cause saline water in the deeper marine formations to migrate into wells.
To balance withdrawals with recharge requires limiting the amount withdrawn to
2,900 acre feet, which in most years would limit the exercise of all claims of
vested rights up to 58%. There are 13 wells in the Tigard plan area portion
of the critical area, most of them clustered on Little Bull Mountain, and with
the exception of the Tigard Water District wells, virtually all of the water
from them is used for irrigati.uz. Only two of them have water rights junior
to the limiting threshold. However, a Tigard Water District well just outside
the plan area boundary also has junior rights.
On May 17, 1974, the state ordered the Tigard Water District to restrict its
withdrawals to 1,060 acre feet per year during 1974, 1975 and 1976. By 1973
the withdrawals of the district had already fallen by 21% from 1970.
Withminor exemptions there were other orders prohibiting any additional wells
from tapping the Columbia River Basalt aquifer within the critical area and
otherwise requiring management of this aquifer to reduce pumping to the
stipulated maximum per year. In 1976, the four wells of the Tigard Water
District yielded only 847 acre feet despite full-tame pumping.
Urbanization does aggravate the pumping of ground water even at the current
rate of usage. Recharge in the Bull Mountain-Little Bull Mountain areawill
be reduced as more of its surface is converted into impervious. cover. The
soil cover and geological formations are poorly permeable, allowing for very
f-,
slow recharge of the basalt aquifer several hundred feet below the surface.
The effects of urbanization will clearly have some negative effect on the
ground water supply, however minor.
-74-
k
k
Appendix E
i
SOILS
The soils covering the Tigard area are derived from the underlying geological
"parent" material, largely wind and water-deposited sediments. They generally
consist of silt loams with surface slopes between 0% and 20%. Their
characteristics are widely varied and thus pose a range of problems and
provide a diversity of opportunities. The Soil A Water Conservation Service
(U.S. Department of Agriculture) has developed maps and detailed data on the
features, suitabilities, and limitations of soils found in Tigard.
i
Based on SCS photo-mosaic maps at a scale of 4" = 1 mile (1"-1320') soils are
being mapped for the Tigard Urban Plan Area. The key to this map is the
following table of soil characteristics, which outlines the primary aspects of
each soil unit such as agricultural capability, drainage, slope, runoff,
shrink-swell potential, septic-tank suitability, and so forth. Comprehension
of the terminology used in the table is aided by reference to the SCS
publication (on file in the Tigard Planning Department) - Soil Interpretations
for Oregon.
The hazard ratings for erosion, landslide, and earthquake ground response are
based on an engineering geology report developed for the adjacent Lake Oswego
area 1.rLlg4neering Geology," Tnt�o I�C47POA' Physical Resources Inventory, 1975).
Many soils are common to both areas. Application of the methods developed
there, the landslide rating system, for example, entailed some calibration,
modification, ,and informal consultation with their author, in order to be
suitable for other soils in Tigard.
t
y _ ,
-75-
See Soil Classifications Inserts
x
-76—
Appendix F �-
i 4.
EXISTING VEGETATION
A detailed botanical inventory of the area was not possible. However, local
residents wi :ib expertise in field identification of native planta voluntarily
surveyed some parts of the community's remaining natural vegetation. George
Jeffcott (Ging City) submitted species lists for Cook Park and Little Bull
Mountain. (see Table IX).
Distinctive Trees
Some trees 'may be of sufficient size to warrant special attention whether they
are native or introduced. Though there has not been a comprehensive survey of
the area to identify major tree groves or individual specimens deserving
preservation or particularly careful treatment, the following are among those
which have been noted:
Two Big-Leaf Maples - Ripleys Farm House Maple Shop, 14170 SW Pacific
(Lois Johnson, Friendly Neighbors Garden Club)
Silver Maple - Gingerbread Cottage, 12185 SW Main (Lois Johnson)
Oregon White Oak Dick's Trailer Shop, 10915 SW Gr€enburg Road (Lois
Johnson)
Redwood - 11990 SW Lincoln (staff)
Sequoia - 9300 SW Center (staff)
s
-77-
Table X
' Vegetation in Cook Park and Little Bull Mountain
Cook Park
Trees: Dougaolas fir Pseudotsuga menziesii
Grand Fir Abies grandis
Western dogwood Cornus nuttallii
Oregon white oak Quercus garryana
Ponderosa pine Pinus ponderosa
Oregon ash Fraxinus latifolia
Western yew Taxus brevifolia.
Cascara, chittam Rhamnus purshiana
Blue elderberry Sambucus cerulea
Red alder Alnus rubra
Western red cedar Thuja plicats.
Shore, lodgepole, pir_e Pinus contorts.
Hawthorn Crataegus (species? dormant)
Oregon, big-leaf, maple Acer macrophyllum
Vine maple Acer circinatum
Shrugs: Creek, red osier, dogwood Cornus stolonifera
Hazelnut Corylus cornuta
Mockorange, syringa Philadelphus lewisii
Burning bush, western wahoo Euonymus occidentalis
CSnowberry Symphoricarpos albus
Wild rose Rosa gymnocarpa
Salmonberry Rubus spectabilis
Thimbleberry Rubus parviflorus
Red huckleberry Vaccinium parvifolium
Wild blackberry Rubus ursinus
Black cap Rubus leucodermis
Salal Gaulti,�ria shallon
Ocean spray Holodiscus discolor
Spirea Spirea douglasii
Indian plum, osoberry Osmaronia cerasiformis
Oregon grap Berberis aquifolium
Poison oak Rhus diversiloba
Service berry Amelanchier alnifolia
Climbers: Western clematis Clematis ligusticifolia
Honeysuckle Lonicera (species?)
Ferns: Sword fern Polystichum munitum
Bracken Pteridium aquilinum
Lady fern Athyrium filiz-femina
Licorice fern Polypodium glycyrrhiza
Not seen but very probably present:
Maidenhair fern Adiantum pedatum
11/76
-78-
Cook Park (cont.)
i'
Ferns: Mullein Verbascum blattaria (introduced)
Nettle Urtica (sp? Probably dioica)
Fringecup Tellima grandiflorum
Trillium, wake robin Trillium ovatum (very large)
False-lily-of-the-valley Maianthemum dilatatum
Unidentified solanum, dormant
Waterleaf Hydrophyllum (probably tenuipes)
Fairy bells or fairy lanterns Disporum smithii or hookeri E
(no bloom)
Fox glove Digitalis purpurea (introduced) !
False solomon seal Smilacina racemosa
i
Inside-out-flower Vancouveria hexandra
Pearly-everlasting Anaphalis margaritacea
Buttercup Ranunculis (So many species, so
similar, nearly impossible to
distinguish)
Queen Anne's lace Daucus carota
Scouring rush Equisetum (Not enough to identify
species)
St. John's wort Hypericum perforatum (introduced)
t.,,.1_,_ ..
Larkspur (tall) ne-r••=j�=�, Probably trolliFoiium
Tansy ragwort Senecio jacobaea (poison to cattle)
Wild strawberry Fragaria vesca
Kennikinnick Arctostaphylos uva-ursi (introduced)
Yellow oxalis Oxalis, probably sucksdorfii ,
Veronica Veronica (species? dormant)
Cat-tail Typha latifolia (field N of park)
Johnny-jump-up Viola glabella (not seer_ but almost
certainly presentin spring)
'
n-,
:a
v'
�u
j� Little Bull Mountain
` Trees: Douglas fir Pseudotsuga menziesil
Big-leaf maple Acer macrophyllum
Vine maple Acer circinatum (few)
Hemlock 'Tsuga heterophylla
Western dogwood Cornus nuttallii p
Cascara, chittam Rhamnus purshiana
Blue elderberry Sambusus cerulea
Red alder Alnus rubra
Western yew Taxus brevifolia
Hawthorn Crataegus (sp?) (Dormant)
Bitter cherry Prunus emarginata, Var. emarginata.
Madrona Arbutus mensiessi (few)
Shrubs: Service berry Amelanchier alnifolia (near tree
size)
Red huckelberry Vaccinium parvifolium
Salal Gaultheria shallow
Oregon grape Berberis aquifolium
Ocean spray Holodiscus discolor
Hazelnut -,-
ryl
rous cornuta
�
Thimble berry Rubus parviflorus
Snowberry Symphorocarpos albus
Blackberry Rubus ursinus
Black cap Rubus leucodermis
Shrubs:. Poison ivy Rhus diversiloba (vine form)
Crab apple (Unidentified, dormant)
Currant (red?) Probably Ribes sanguineum. Dormant
Wild rose Rosa gymnocarpa
Honeysuckle Lonicers (Sp?)
Ferns: Sword fern Polystichum munitum
Bracken Pteridium aquilinum -
Wood fern Dryopteris austriaca
Licorice fern Polypodium glycyrrhiza
Small'' Plants:
Inside-out-flower Vancouveria hexandra
Fairy bells orfairylanterns Disporum smithii or Hookeri
(No bloom)
False solomon seal Smiiacina racemosa
Bird bill, geranium, Geranium, probably molle
(introduced)
Trillium, wake robin Trillium ovatum (exceptionally
large)
1 Johnny-jump up Viola glabella
Foxglove Digitalis purpurea (introduced)
.j,
_g0—
Appendix G
WILDLIFE
The Oregon Department of Fish and Wildlife conducted a general habitat survey
or the area in September, 1476. On the basis of general knowlEdge of
terrestrial and bird species round in similar areas nearby, a lint of animals
which could be expected to occur was compiled, together with information about
their habitat requirements. Though some species have recently been observed
which are not on the list (e.g. deer on Bull Mountain), this enumeration
includes those most likely to be seen.
r
F
l
-81-
Table XI
Inventory of wildlife Species
MAMMALS
Species Habitat Requirements Remarks
Chickoree woodlots
California ground brush, cropland
squirrel
Raccoon riparian
Schrews woodlots, brush
Deer mousewoodlots, brush
Striped skunk brush, riparian
Nutria riparian introduced species
Oppossum riparian, urban introduced species
Brush rabbit brushy areas, riparian
House mouse urban, brush
Little brown bat riparian, woodlots
Muskrat riparian
Mink riparian
Weasel riparian
Beaver riparian
Black-tailed deer woodlots, riparian
Coyote woodlots, riparian
Red fox fields, brush
Pocket gopher fields
Gray fox fields, brush
REPTILES
Species Habitat Requirements Remarks
Alligator lizard brush
Rubber snake brush
Garter snakes fields, brush
Western painted turtle riparian
AMPHIBIANS
Species Habitat Requirements Remarks
Rough skinned newt riparian
' Salamanders riparian
Western toad riparian
Bed-legged frog riparian
Tailed frog riparian
Pacific tree f rog riparian'
Bullfrog riparian
-82-
}
BIRDS
Habitat Requirements Remarks •
Spe'__
ponds,marshes, rivers nest in colonies
Great blue heron ponds, grassy fields
Canada goose pviae, marshes: riparian nest in area
w.,
Mallard ponds, marshes, riparian
Pintail ponds, marshes, riparian may nest in area
Cinnamon teal ponds, marshes, riparian
Blue-winged teal ponds, marshes, riparian also like to feed
American wigeon on park lawns
!C
ponds, marshes, riparian
Northern shoveler deeper ponds & lakes dive for food
Ring-necked duck dive for food t
deeper ponds & lakes dive for food
Canvasback deeper ponds & lakes
Lesser scaup deeper ponds & lakes dive for food
Buffle headdeeper ponds & lakes dive for food
Ruddy duck lakes and rivers
Common merganzer riparian nest in tree `
Wood ducks cavities
open farm & forested
Turkey vulture areas f,
open country, farms
open country, farms rare winter visitor
Red-tailed hawk
1
Rough-legged hawk farms most cor, )n
open country,
P.merican vestrel
I Cooper's hawk brushy areas
`_ � open agricultural land brush
Afars« itcdn� farmlands with adjacent
Ring-necked pheasant farmlands with adjacent brush ;
California quail °
grassy areas near water
Killdeer wet meadows
Common snipeadapt well to man f
agricultural lands,
Gull garbage dumps e
use mineral springs
forest areas
Ban-tailed pigeon farmland
Mourning dove brushy areas
Screech owl
Great horned owl brushy areasriparian feeds on small
Belted kingfisher fish
forest & open areas
feed Common nighthawk. lants ed on plant
Rufous hummingbird
need flowering p nectar
Common flicker forested areas, riparian
deciduous trees
Yellow-bellied sapsucker deciduous trees
Downy woodpecker brush, riparian
Traill's flycatcher grasslands
Horned lark varied, catch flying
Cliff swallow insects
varied, catch flying cavity nester
Violet-green swallow insects
cavity nester
Tree swallow varied, catch flying
r insects
varied, catch flying
Barn swallow insect
53
t
Species Habitat Requirements Remarks
� r
Rough-winged swallow varied, catch flying
insects
Steller's jay brush
Common crow farmland
Common bushtit brush
Black-capped chickadee deciduous trees
Red-breasted nuthatch conifers
White-brested nuthatch deciduous trees
Winter wren brushy areas
Bewick's wren brushy areas
House wren brushy areas cavity nester
t
American robin varied, like lawns-parks
Varied thrush brush & forest
Swainsons thrush mixed .:onifers &
deciduous brush
Ruby-crowned kinglet brush
Golden-crowned kinglet conifers
Cedar waswing brush, farmland
Warbling vireo brush
Yellow warbler riparian
■
Common yellow-throat-throator„sh; wet areas
--
Mac Gilliuroy's warbler low growing brush
orange-crowned warbler brush c
Yellow-rumped warbler brush, riparian
Starling farmlands, riparian
House sparrow urban crowd out native
birds
Red-winged blackbirds farmlands
Cowbirds farmlands
Western meadowlark open grasslands not compatible
with residential
developments
Black-headed grosbeak riparian, brush
Evening grosbeak trees with seeds usually seen in
flocks
Purple finch mixed conifers &
herdweeds
House finch shrubs, cropland adapt well to urban `
areas-thistle
American: goldfinch trees, brush, weeds thistle & dandelion
important food
Lazuli bunting brush, open areas
Rufuous-sided towhee thick brush
Chipping sparrow open woodlands ,
White-crowned sparrow open woodlands t
Golden crowned sparrow open woodlands
Song sparrow brush patches
Fox sparrow brush patches
-84-
The following list of birds were seen within Tigard during a survey taken in
1978. The survey includes migratory species as well as species now infrequent
in the area.
Table Xii
GREBES PIGEON
Pied-billed Grebe Band-tailed Pigeon
Mourning Dove
HERONS AND BITTERNS
OWLS
Great Blue Heron
Black-crowned Night Heron Screech Owl
Great Horned Owl
SWANS, GEESE, DUCKS Pygmy Owl
Saw-whet Owl
Whistling Swan
Canada Goose HUMMINGBIRDS
Mallard
pintail Rufus Hummingbird
VULTURES, HAWKS, EAGLES KINGFISHERS
Turkey Vulture Belted Kingfisher
Shark-skinned Hawk
Red-tailed Hawk WOODPECKERS
k FALCONS Red-shafted Flicker
Pileated Woodpecker
Sparrow Hawk Yellow-bellied Sapsucker
Hairy Woodpecker
QUAIL Downy Woodpecker
Bobwhite TYRANT FLYCATHERS
California Quail
Ring-necked Western Wood Pewee
CRANES SWALLOWS
Sandhill Crane Violet-green Swallow
Tree Swallow
RAILS AND COOTS Barn Swallow
Coot CROWS AND JAYS
PLOVER, TURNSTONES, SURFBIRDS Steller's Jay
Scrub Jay
Killdeer Common Crow-CP
f
t
-85-
CHICKADEES AND BUSHTITS WOOD WARBLERS, YPLLOWTHROATS,
CHATS
Black-capped Chickadee
Chestnut-backed Chickadee Yellow Warbler
• Common Bush-tit Myrtle Warbler
Audubon's Warbler
NUTHILTCHES Yellowthroat
-� Yellow-breasted Chat
White-breasted Nuthatch
Red-breasted Nuthatch MEADOWLARKS, BLACKBIRDS,
ORIOLES, COWBIRDS
CREEPERS
Western Meadowlark
Brown Creeper Red-winged Blackbird
Brewer's Blackbird
WRENS Brown-headed Cowbird
House Wren TANGERS
Bewick's Wren
Long-billed Mash Wren Western Tanger
THRUSHES GROSBEAKS, FINCHES, SPARROWS,
BUNTINGS
Roin
Varied Thrush Black-headed Grosbeak
Hermit Thrush Lazuli Bunting
Swainson's Thrush Evening Grosbeak
Western Bluebird Purple Finch
House Finch
KINGLETS Pine Siskin
American Goldfinch
Golden-crowned Kinglet Lesser Goldfinch
Ruby-crowned Kinglet Rufuf-sided Towhee
Slate-colored Junco
WAXWINGS Oregon Junco
Chipping Sparrow
Cedar.Waxwing White-crowned Sparrow
Golden-crowned Sparrow
SHRIKES Fox Sparrow
Lincoln Sparrow
Northern Shrike Song Sparrow
STARLINGS
Starling
VIROES
Hutton's Vireo
WEAVER FINCHES
English Sparrow
-86-
The Oregon Department of Fish and Wildlife also identified game, fish found in
the Tualatin River, Fanno Creek, and Summer Creek: ,7
Table XIII
Fish Found in Tigard-Area Streams `
Game Fish Species Tualatin Fannn R..n....e.. r�
River Creek v(lakes)�•
Fall Chinook Salmon Oncorhynchus Tshawytscha S
Coho Salmon Oncorhynchus Kisutch M
Winter Steelhead Trout Salmo gai.rdneri M
Cutthroat Trout Salmo clarki M S
Channel Catfish Ictalur_,us nunctatus R R
Brown Bullhead Ictalurus nebulosus R S
Yellow Perch Perca flavescens R S
Largemouth Bass Micropterous salmoides R R
Warmouth Bass Lepomis gulosus R R
Bluegill Lepomis marcrochirus R R
White Crappie Pomoxis annularis R S
Black Crappie Pomoxis nigromaculatus R S
Crayfish Pacifieastacus
gyp• R R
Nongame Fish Species
Carp Cyprinus_carpio R R
Northern Squawfish Ptychocheilus ore onensis R R
Largescale sucker Catostomus macro
cheilus R Rr
Redside Shiner Richardsonius balteatus R R
- Higrarory R Resident S = Suspected
Cutthroat trout have recently been observed in
Ash Creek, which is surprising
considering the severly degraded water quality of the stream. Rough fish have
t
been observed in smaller streams (e.g. Redrock Creek).
1
Y
-87-
APPENDIX H
EXISTING PARKS, GREENWAYS AND RECREATION
L
Within the incorporated boundaries of Tigard, the City currently owns 92.72
acres of park land.
In addition to the recreation space provided by the City parks, there are
several acres of recreational space provided by the local schools (See
Table XVI). There are also 201 acres of floodplain and wetlands classified by
the City's Comprehensive Plan as "Greenway" or non-buildable for urban
development. They are, however, suitable for pathways and non-intensive
recreational uses. The City has acquired, through dedication and purchase,
37.90 acres of greenway property. Within the City, the combination of City
park land, school recreational space and greenway provides a ration of
recreation and open space in excess of the National Recreation and Parks
Association standard of 10 acres of park land per 1000 people. When the
current population (approximately 17;000) is considered as probable users of
local facilities, the ratio is 12.15 acres of potential parks and open space
available per 1000 people.
Table XIV
PARKS
Acres
Cook Park 46.28
Woodard Park 3.26
' Jack Park 9.22
Summerlake Park 15.75
Englewood Park 15.16
Liberty Park .54
Ye Old Windmill Park 1.11
Scheckla Park 1.40
Fanno Creek Park 32.50
(Not accepted but owned by City)
125.22 acres
88-
Table XV
GREENWAYS
Acres
S.W. Grant 0.15
S.W. Tiedemar. 0.10
Clydesdale (Tract "A") 0.26
Terrace Trail 5.39
' Knute Quale 5.08
(Hall Blvd. Fanno Creek area)
Tibbett Place 0.67
Pathfinder 412 0.28
Black Bull 2.91
Hollytree (Tract "A") 1.15
Genesis 0.05
Genesis 412 1.10
Pick's Landing 411 1.27
Pick's Landing 412 2.64
Genesis 413 3.42
Yolo Estates 0.10
Fanno Creek Park 1.71
(Lot 413, Burnham Tract)
Bellwood 413 0.40
Tigard Senior Citizen's Center 3.09
(Tax Lot 600)
Brookway Tracks B 6 C 6.55
:reek Side Park 0.8i8�
TATAT
MAL ACRES 37.90
I
v .I
-89-
jm. .
Table XVI
SCHOOL SITE*
'Y Charles F. Ele. 9.20 Tigard #23J
St. Anthony's 6.88 St. Anthony's
Woodward Elem. 8.88 Tigard #23J
Fowler Jr. Hi. 54.00 (north Tigard Hi undev.) Tigard #23J
Templeton E.em. 12.62 Tigard #23J
Twality Jr. Hi. 15.41 Tigard #23J
Tigard Sr. Hi. 49.56 Tigard #23J
Durham Elem-_ 5.35 Tigard #23J
Phil Lewis Elem. 3.49 Tigard #231
Englewood Elem. 7.10 (undeveloped) Beaverton #48
Total School 172.5
* Excludes City shop area. Approximately 40% of each school site is occupied
by buildings leaving 602; in various forms of open space. There is also some
space within the structures which are used for (indoor) physical education.
Therefore, for purposes of computing available open space, a 60% figure has
been used yielding approximately 10.3 acres of open and recreational area
provided by local schools.
Inventory of City Parks
I. Liberty Park: This facility is a .54 acre mini-park located in the
(" downtown core area at the east end of Main Street. The park was created
v by the realignment of Main Street to accommodate a 900 alignment to
Pacific Highway at Greenburg Road. The site is essentially a landscaped
area but has a walkway length-wise through the center of the site with
three benches and a bus stop shelter provided.
2. Woodard Park: This neighborhood facility is located on Fanno Creek in the
southern portion of Neighborhood Plan Area #3 (NPO #3). The site consists
of 3.5 acres of floodplain property and is heavily wooded with deciduous
trees.
The entire site is cleared of underbrush and has been planted in grass.
Other improvements include a landscaped entrance and bridge, off of SW
Johnson Street, paved walkway, lighting and playground equipment. Future
improvements planned are the addition of two picnic tabl€>s.
3. Jack Park: This neighborhood park is located in the southwest portion of
NPO $7 in the Bellwood Subdivision on SW Walnut S`.reet. The site consists
of 12 acres which for the most part slopes to the east towards an unnamed
creek which meanders through the park. Portions of the site have fairly
steep slopes down to the creek channel, limiting use of these areas, there
is a small stand of fir in the southeast portion of the park along the
creek bank.
- J
Improvements to the site include lawn and landscaping, paved pathways,
lighting, play equipment and restrooms, two barbecue stands and five
picnic tables
Future improvements planned include tree planting, construction of a ball
field and backstop, landscaping and westerly side of the park and because
of excessive vandalism problems, and because of' the neighborhood character
of the park the restrooms may be converted to ar equipment storage area.
-90
4. Cook Park: Thisacili`y is classified as a large urban park and is
located just south of, Tigard High School, along the Tualatin River in the
soutneast corner of NPO #6. The site consists of 50.3 acres (35.8 acres
developed and 14.5 acres undeveloped). The entire site is in the t
floodplain of the Tualatin River and is heavily wooded along the river and
the southeast portion of the park.
Improvements to the site include a paved road throughout the park, three
paved parking areas plus several areas for shoulder parking, a landscaped
entrance, lawn, refreshment stand (operated by the Tigard Little League),
lighting for twoo ball fields, play equipment (swings, teeter-totter,
slide, etc.) a covercd shelter area with no er ntztlets. nine small
barbecue stands, o.xe large barbecue pit, fifty picnic tables, four
drinking fountains, izatrooms, boat launch ramp and dock, natural area
with trails, and the Mary Woodard Memorial Maple Grove.
Future development plans include installation of six benches in the play
and picnic area, and for the undeveloped 14.5 acres, construction of two
soccer fields, multi-use open area, additional paved parking area, a
second restroom facility, an archery range and horse shoe pits. Water
front improvements, flood control (channel clearing, etc.), tennis courts
and other improvements are being considered.
5. Summerlake Park: This facility is considered a community park and is
located south of SW Scholls Ferry Road and east of SW 130th Avenue. The
site consists of 15.75 acres, a portion of which will include a lake for
flood and storm water retention. The site at this time is devoid of any
major forested areas.
Proposed improvements to the site will include tennis courts, ball fields,
walkways, seating, restrooms, pic^.ic areaS and nark offices with
landscaping throughout the site. Currently, there is aY bridge across the
lake, however, none of the other improvements have been made to park site.
6. Englewood Park: This community park facility menders through the
Englewood subdivision adjacent to Fanno and Ash Creeks. For the most
part, this park is unimproved except for extensive bikepaths and various
play equipment. The remaining park area consists of various riparian
vegetation which harbors various aquotic and bird populations.
7. Ye Old Windmill Park: The neighborhood park serves more as a community
landmark rather than a functional park facility. The semi-restored
windmill serves to remind Tigard's residents of the typa of life styles
that preceded the Tigard that its residents know today.
8. Scheckla Park: This is currently an undeveloped proposed neighborhood
park. It is anticipated that the area of this park will expand to the
west to encompass the pond as the westerly property is developed.
9. Fanno Creek Park: This is currently an undeveloped proposed eighborhood
P
park located along the south side of Fanno Creek just north of O'Mara. A
portion of the park will remain in its natural state and the developed
portions of the park will include softball/soccer field, multiple purpose
paved area, picnic area with shelter, restrooms, and-a small parking area.
91-
Existing Recreation Programs
The City of Tigard currently does not sponsor any formal recreation programs.
All such programs, now in existence, are offered either through Tigard or
Beaverton Srhool Districts, Tualatin Hills Park and Recreation District, or
local independent leagues (e.g. baseball/softball, basketball and soccer
leagues with City and School District facilities).
The School District offers the traditional inter-scholastic sports programs,
e.g. basketball, baseball, football, etc. during the academic year.
Intramural sports are also offered for the general student population special
are offered
cdrastion programs --r handiranAPd and retarded children)
year-round. The special education program is sponsored by an independent
organization but uses school district facilities. The district's summer
school program also offers basic instruction in several sprots as well as arts
and crafts.
The Tigard swim center offes a wide variety of programs through the schools as
well as for the general public. The offer adult lessons, school instruction
programs, summer instructions private lessons, water polo (high school),
aquatic classes (including junior and senior life saving), and adult and
family swim sessions. The center is operated on a year
basis and is the
j' most heavily used facility in the City.
Plans to Meet Future Needs
Until August 1977, the City of Tigard had no formal parks system. It also had
no organized program for developing such a system and still does not have any
recreation program. The existing parks were acquired on an individual basis
through the dilegent efforts of a few interested local residents as well as
through the subdivision process.
The rapid population growth and the subsequent increased need for open and
recreation space required that the City develop a more systematic approach to
parks development. In August 1977, the City adopted the "Environmental Design
and Open Space Plan" as an element of the City's Comprehensive Plan. This
Plan established standards and policies for the development of a city-wide
park and recreation system.
The plan established a goal to maintain 10 acres of parks and open space per
1000 people as the City continues to grow. Recreational space, facilities and
programs are planned to be provided through a coordinated effort with the
local school district. The City's Park Board membership was modified to
incorporate a representative from the School District.
As an initial Plan implementation measure, the City adopted an ordinance which
assesses a fe (system development charge) on the issuance of all residential
building permits. The fees collected are placed in a park acquisition and
development fund. The system development charge is based on the ratio of 10
acres p« 1000 people set by the Plan and provides seed money for matching
grants and bond retirement.
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The Park and Open Space Plan assumes that the unincorporated areas within the
Plan area will eventually be annexed to the City. Therefore, projected needs
for park and recreational space are based on Plan area population
projections. Even if some areas remain unincorporated, residents of these
areas will likely benefit from the City facilities. The initial draft of the
Capital Improvements Program will be based on the following:
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System Development Charge
In August 1977, the City adopted an ordinance assessing a fee on all
resident-4--l- building permits. The fees collected are earmarked for
acquisition and development of the City's Park and Recreation system. The
basic concept behind the charge is the increased demands on park and
recreation facilities, and is generated by occupants of new developments.
therefore, they should assume a portion of the burden of financing new
recreation facilities. In addition, several acres of parks and open space
land have been dedicated to the City in lieu of payment in cash. Following
the defeat of the City's tax base proposal (May 23, 1978), the majority of
funds originally allocated to parks development were cut from the proposed
fiscal year 1978-79 budget. The only funds remaining in the budget will be
those collected from system development charges.
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APPENDIX I
CITY OF TIGARD, OREGON
ORDINANCE NO, 82—YL_
AN ORDINANCE OF THE TIGARD CITY COUNCIL iu"SENDiNG C:tAFTER 3.16, DEVELOPMENT
CHARGES -- RECREATION FACILITIES, OF THE TIGARD MUNICIPAL CODE; AND FIXING AN
EFFECTIVE DATE.
THE CITY OF TIGARD ORDAINS AS FOLLOWS:
SECTION 1: The Tigard City Council finds it necessary and prudent to update
the language in Chapter 3.16 to reflect the Tigard Comprehensive
Plan Element and to allow purchases of major park maintenance
equipment from the Park SDC Fund, and thus repeals Chapter 3.16,
Development Charges --Recreation Facilities of the Tigard
Municipal Code in its entirety and replaees Chapter 3.16 with the
attached Exhibit "A", to read as follows:
SECTION 2: This ordinance shall be effective on February 1, 1983; provided,
however, that the Council shall review TMC Chapter 3.16 at its
first regular meeting in October 1983.
PASSED: By the City Council by vote of all Council members
present after being read by number and title only, this e2 o day
(( Of Do car., b 1982.
City "Recorder - City of Rard
Approved: By the Mayor this o2cJ day of ,Upc c,e, 1982.
'
Mayor —City of Tigard
ORDINANCE NO._82- °y
(0447A)
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Cheater 3.16 ,
DEVELOPMENT CHARGES--
RECREATION pACTLITIES
Sections:
3.16.0010 Charge 'Imposed-purpose.
3.16.020 Definitions.
3.16,030 Formula for determining charge.
3.16.040 Payment.
3.16.050 Exemptions.
3.16.060 Dedications in lieu of fees.
3.16.070 Park and recreation development fund.
3.16.080 Appeals.
3.16.090 Scope--Construction.
3.16.010 Charge imposed--Purpose. A system development charge is hereby
imposed to acquire, develop, and expan%: additional park and recreation
facilities and the purchase of major park and recreation maintenance equipment
as defined in Section 3.16.020, and shall be collected in connection with the
development of all residentially designated properties within the City of
Tigard, as provided in the Tigard Comprehensive Plan.
3.16.020 Definitions. For the purpose of this chapter, the following
definitions and their derivatives shall apply; _
facilities" means tho94 areas and
facilities deemed necessary for public health, safety, and general welfare to
maintain an adequate level of recreational space and facilities as specified
in the Natural—Features and Open Space Element of the Tigard Comprehensive
Plan. Said areas and facilities include bu;l are not limited to parks; open or
undeveloped land suitable for passive or active recreation; pathways; swimming
pools; play courts; playgrounds; and gymnasiums.
- (2) "Building permit" means any permit issued under ORS 456.750 to
456.950.
(3) "Development" means and includes:
(A) The establishment of a residential use of any parcel of land or
the construction or the placing of a structure upon a parcel not previously
occupied by any residential structure;
(B) Any alteratinn or change in use which increases the number of
parking spaces required pursuant to Title 18 of the Tigard Municipal Code; or
(C) The resumption of use after a period of non-use Pxccading-one
year which the City Council may find creates a substantial likelihood of �.
increasing the need for parks or park facilities.
(4) "Major park and recreation maintenance equipment" means any
aubstantial acquisition in excess of $5,000 of equipment, or components
thereof for use in maintaining parks and recreational areas.
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3.16.030 Formula for dot rmining c*i,k-_ (a) The following formula has
been used as the basis for determining the system development charge:
' System Development Charge Formula
A X P X $ - 3
(A) - Park acreage standard (From Natural Features and
Open Space Element)
*(P) = Average number of people per unit
**($) - Average sale price of reeidenti:l land
(S) System charge
*The present (1980) average number of people per household as verified by
Portland.State University's Center for Population Research are as follows:
Single-family - 3.28
Multi-family - 1.95
Mobile home - 1.61
**The present average sale price of unimproved residential land as
estimated by Washingtor. County's office of assessment and taxation is $9.500
p--r acre.
Using these figures and the Natural Features and Open Space Element
standard of one acre of park for every one hundred people and an average
( appraised value of residential land of $9,500/acre**, the fee assessed per
i unit would be as follows:
w Sinble-family Mobile RnmP
1 ac/100 X 3.28 X $9,500 .01 X 1.61 X $9,500 .01 X 1.95 X $9,500
.01 X 3.28 X $9,500 _ .0161 X $9,500 .0195 X $9,500
.0328 X $9,500 ;152.95 = $185.25
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(b) The system development charge is imposed upon the development of all
lands in the City of Tigard, according to the demands which the proposed
development of said lands place upon the park and recreation system serving
the City as described above. Charges are set at one-third of the figures
derived from the formula set out In subsection (a) of this section and rounded
to the nearest even ten. Thus the charges to be rnade are as follows:
(1) Single-family residential unit $100.00;
(2) Multi-family residences 60.00 per unit;
(3) Mobile homes 50.00 per space.
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3.16.040 Payment. The system developnent charge 3hr_11 be immediately due
and payable upon development. including receipt of an application for a
residential building permit. The applicant for such permit shall pay ,and the
building official shall collect the applicable system development charge prior
to issuing ,any building permit , for any new construction or additions.
.% alterations or changes ,in use which creates a;dwelling unit as defined in this
title. The building official_ shall decline to issue- any such permit until
such charge has been paid in full.
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3.16.060 S;emptions. The following properties shall be a::mpt From the 4
charges imposed In Section 3.16.030:
(1) City-owned land;
(2) Any Bingle dwelling unit on a lot of more than one acre in site;
(3) Any parcel of land which ties an established use is exempt from the
system development charge to the extent of any structure then existing on the
land or covered by a building permit issued on or before August 11, 1977.
3.16.060 Dedications in lieu of fees. (a) Developers 'Of subrivistons
who apply for several building permits simultaneously with preliminary or
final plat approval shall be afforded the option of dedicating land in lieu of
the system development charge under such conditions as may be provided by the
approval authority under such plan and this title. Any such offered
dedication may be accepted only if the land offered can be used for
recreational purposes in a manner consistent with the Natural Features and
Open Space element of the Tigard Comprehensive Plan; or if the land is to be
sold by the City to obtain funds for such purposes pursuant to such element;
and provided further that such land has not been used to obtain a density
trade-off in a planned development pursuant to TMC Title 18.
However, no dedication shall be accepted for land which, according to the
Natural Features and Open Space Element of the Tigard Comprehensive Plan, is
inadequate in size or unsuitable in location or topography for the facilities
necessary to satisfy the needs of the new City residents.
(b) If any dedication does not fulfill the required system development
charge for the number of units in the subdivision, as set forth in Section
3.16.030, a fee shall be collected to make up the difference. The formula and
average cost per acre of unimproved residential property, as defined in
subsection (a) of Section 3.16,030, ehmil be kept on file by the building
official and updated annually by Council Resolution. One-third of this cost
per acre shall be used as the standard for determining the value of any land
dedicated in lieu of the system development charge.
(c) Credit against the system development charge shall be given for
additional park and recreational facilities provided within the developme--it or
at an established recreation site provided that such facilities will at all
times be available and accessible to the general public, and provided further
that the approval authority determines such facilities to be necessary to
serve the needs of the public, as provided in the Natural Features and open
Space Element of the Tigard Comprehensive Plan.
3.16.070 Park and recreation development fund. There is hereby created a
dedicated fund entitled "Park and Recreation Development Fund." All funds
derived from the system development charge provided by this chapter shall be
placed in one of two pack and recreation development district funds and be
segregated by accounting practicss from all other funds of the City. Pacific
Highway (designated State Highway 99W) shall serve as the dividing line for
the creation of the two park and recreation development districts. All °
revenues collected on account of park and recreation fc::ilities shall be
placed in the fund and expended for acquisition or development of additional
park and recreation facilities within the district in which$ they are
collected. Any expenditure of funds for major park and recreation maintenance
equipment shall be expended equally from each district if use_2 on a citywide
basis; otherwise, much expenditures shall be pro-rated by anticipated use of
the equipment. All such funds shall be used for no purpose other then those
activities necessary for acquisition, development or expansion of recreational
facilities as defined in Section 3.16.020.
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3,16.060 APPeals. Any person who is aggrieved by any decision required
or permitted to be made by thea Cicy Administrator. Planning Director or
+ Building official under this chapter may appeal that decision to the City
Council by filing a written request with the City Recorder describing with
particularity the decision of the officer from which the person appeals. En
considering the appeal. the Council shall determine whether the decision In
correct and may affirm. modify. extend or overrule that decision.
3.16.090 Scope--Construction. tit) The system development charge
provided in his chapter is separate from and in addition to any applicable
tax, assessment, charge. or fee otherwise provided by lay.
(b) The rules of statutory construction provided in ORS 174.010 through
174.110 are adopted and by this reference made a part of this chapter.
(G44%A)
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Bibliogrdp::y
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■ Or-
4 Hydroloogy, Flooding and Groundwater
s
' Data
Flood Plain Information- lualatin River and Tributaries, Washington
County, Oregon, U.S. Army Corps of Engineers, June, 1969.
Geology and Groundwater of the Tualatin Valley, Oregon, D.H. Hart and R.C.
Newcomb, U.S. Geological Survey, Geological Survey Water Supply Paper
#1697, 1965.
"Cooper Mountain-Bull Mountain Critical Ground Water Area: Findings,
Conclusions, and Order by the State Engineer of Oregon," Chris L. Wheeler,
May 17, 1974. -
Tualatin River Basin Survey Water Quality Project, OMSI, Metropolitan,
Schools, Environmental Protection Agency, Oregon Department of
Environmental Quality, June, 1976.
"Tigard, Tualatin Hit with Flood Conditions," Tigard Times, January 24,
1974.
Management
Urbanization and Environment, Thomas R. Detwyler and Melvin G. Marcus,
Duxbury Press, 1972.
r "Sediment Problems in Urban Areas," Harold P. Guy, U.S. Geological Su rvev
Circular 601-E, 1970.
Washington County Storm Drainage Master Plan Technical Advisory Committee,
"Report and Recommendations," P-xgust 28, 1975.
"Regulations forFloodPlains," Jan A. Kusler and Thomas M. Lee, ASPO
Planning Advisory Service Report #277, p. 87, February, 1972.
!1
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Geology and Sails
Data Oregon, D.H. Hart and R-C,
the Tualatin Vical Survey Water Supply Pape`
Gealo^` and
Groundwater is I€ Survey, Geolog
Newcomb, U•S. Geolog
#1697, 1965. Herbert G. Schlicker
of the Tualatin Valley Region,
Geology g p and Mineral Industries,
Engineering Ore on Department of Geology
and Robert J. Deacon,
Bulletin 603 1967. Trimble, U:S•
Ore on and Adjacent Areas, D.E.
Geolo of Portland, 1119, 1963.
Geological Survey Bulletin portland=
the Mar uam bill Area, planning
for Planning of Portland
Geology Investigator) , ,-ies, 1973•
Environmental (Principal
Oregon, Robert Redfern Geology
and Mineral Indust_
Commission and Oregon Department of Ge
I Lake Oswego, Ph sica7 Resources Inventory,
c._Lch, 1976.
City of Effects of
o� the Ground et
Geological Investigation Oregon, „Paul Hammond,
++A Preliminary olitan Area, and Mineral
Earthquakes in the Portland Met Department
of Geology
Geological Survey and Oregon P
al. , U.S• 1974.
Industries, Hi hway
South Ti and Interchan e/Pacific Highway
Statement, Federal g
North Ti and Interchan e Im ace 1876.
rate 5 Draft EnvironmentaDivision, November,
Inters-_ State Highways
Administration and Oregon U.F.
Geai�t;" _
Willamette Valley," Ira Allison,
"Glacial Erratics in the 46, 1935.
Orf America Bullet—, Vol• „ James Stauffer,
Societ
Flood Deposits Oregon Country Newslettin the Portland, . Area, 20_31.
"Late Pleistocene erVol. 22, 1956,
Geological Society riculture)
Soil Conservation Service (U.S. Department of Ag
1, Soil Maps
2, Soil Series Interpretation Sheets
3, "Soils Interpretations for Oregon
Sheets,,
Groh,
potential in Oregon y
Edward A. "Geothermal Energy
, Orf gin, Vol. 28,
��7, July, 1966, PP- 125-135• 2—re
Donald A. and Newton, V.C. , Jr.
"Geothermal Activity in 1975,"
Hull, January, 1976, PP•
10-17.
Bin, Vol. 38, SP1, Willamette
of the Lower Col aartment Geol.
V.C. , Jr, , Subsurface Geo zm� ations No. 2, Oregon Dep
Newton, Oil and Gas Investig
Bas,
Is. Oregon,
and----Miner al Indus. , 1969.
th.�_
Newton, V.C. , Jr, , "Oil and Gas Exploration in Oregon, Ore Bin, Vol. 31,
#1, January, 1969, pp. 11-20. ^'
Sand and Gravel Resources, Portland, Metropolitan Planning Commission,
1964.
Management
Performance Controls for Sensitive Lands: A Practical Guide for Local
Administrators, Charles Thurow, et al. , ASPO Planning Advisory Service,
Report 11307 + 308, 1975.
"Application of Land-Use Constraints in Oregon," Leonard Palmer,
Geological Society of Americ, , Special Paper 174, 1976.
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vegetation and Wildlife k
Natural vegetation of Oregon and Washington, Jerry F. Franklin and C.T. j
Dyrness, U.S. Department of Agriculture, General Technical Report; 1973.
Field Surveys j
Lynn Cornelius, Field Biologist, Nature Conservancy, December, 1976.
Gene Herb, District Wildlife Biologist, Oregon Department of Fish and
Wildlife, September, 1976.
George F. Jeffcott, area ret;':dent, November, 1976
Catherine Armand, area resident, Fall, 1976
Lois Johnson, President, Friendly Neighbors Garden Club, October, 1976.
Ruth Kincheloe, Past President (1976), Portland Audubon Society.
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