Impact Study Westlake Consultants, Inc.
IMPACT STUDY (pursuant to Section 18.390.040.B.2.e.)
Application requirements include an Impact Study(study). The study shall quantify the effect of
the development on public facilities and services. The study shall address, at a minimum, the
transportation system, including bikeways, the drainage system, the parks system, the water
system, the sewer system, and the noise impacts of the development. For each public facility
system and type of impact, the study shall propose improvements necessary to meet City
standards and to minimize the impact of the development on the public at large, public facilities
systems, and affected private property users. In situations where the Community Development
Code requires the dedication of real property interests, the applicant shall either specifically
concur with the dedication requirements, or provide evidence, which supports the conclusion
that the real property dedication requirement is not roughly proportional to the projected
impacts of the development.
Discussion of Effects of the Development
1. General Statement
The subject property is located within the R-3.5 Low-Density Residential zone of the City
of Tigard Comprehensive Plan. The subject site has residential uses in close proximity.
To the south of the site one finds many existing lots of 10,000 square feet or larger, as
allowed by the existing zoning. To the north of the subject property zoning transitions to
higher density R-12, which is reflected by an existing apartment complex and smaller
residential lots. There are also a number of larger lots scattered through the area. The
subject property is an infill development parcel constrained by surrounding
development.
2. Transportation System, including Bikeways
a. Effect on public facilities and services
The proposal is for a 10-lot subdivision with a net increase of 9 detached single-family
homes within the subject property. At 10 vehicle trips per day per residence, this will
add an estimated 90 additional vehicle trips per day, which will be directed onto SW
103rd Avenue. The Tigard Transportation System Plan identifies SW 103rd Avenue as a
neighborhood street, which intersects with SW McDonald Street approximately 700 feet
north of the subject property. SW McDonald is designated as a Collector street. The
proposed street, SW Jason Ln., is classified as a Local street.
According to the City of Tigard Transportation System Plan, local streets are designed to
encourage a reduction in trip length by providing connectivity and limiting out-of-
direction travel, while neighborhood routes are for directing vehicles into and through a
neighborhood. Collector streets provide city-wide connectivity. The proposed
subdivision maintains this hierarchy. All of the homes are provided access onto SW
Jason Ln. a local street, which then feeds into a neighborhood route, SW 103rd Ave.
From here all traffic can disperse through the neighborhood to gain access onto SW
McDonald, a nearby collector, for city-wide travel. The proposed public street, SW Jason
Ln., will be dedicated to the city for public use and constructed to city standards.
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1/2 street improvements will be made to SW 100th Ave., including the construction of a
sidewalk, curb and gutter. These improvements will have a positive impact on the City's
transportation system and help to fulfill the goals outlined in the Tigard Comprehensive
Plan.
b. Improvements to meet City standards
The proposal includes plans for the half street improvements along the subject
property's frontage on of SW 100th Ave. to meet applicable development standards. The
developer will also construct the local residential street within the proposed
development consistent with applicable development standards.
c. Impact minimization
The proposed street improvements are consistent with the functional classifications of
SW 100th and SW Jason Ln. By making improvements along SW 100th Ave. this
development will benefit all users of this street. The proposed street design is aimed at
improving traffic safety. Re-alignment and widening of the intersection, along with new
signage to control intersection movements, will aid in slowing vehicles, improve sight
lines, and improve drainage patterns to keep the street free of runoff, debris, or
occasional ice. The construction of improvements according to applicable standards will
mitigate any potential negative impacts on the public at large, public facilities systems
and private property owners.
3. Drainage System
a. Effect on public facilities and services
The proposed development will replace some pervious areas (lawn, etc.) with
impervious surface areas (road, driveways, roofs, etc.). The proposed development will
include a stormwater quality treatment and detention facility consistent with Clean
Water Services (CWS) requirements. This is consistent with the master planning for
surface water management within this drainage sub-basin.
b. Improvements to meet City standards
Storm water runoff from the proposed lots and streets will be directed into a water
quality and detention facility, designed to mimic pre-development conditions, located in
the northeast corner of the subject property within a tract dedicated for this purpose.
Stormwater quality and detention will be achieved through the use of a new water
quality and detention facility (Extended Dry Basin). Runoff from the street as well as
roof drains will be collected in system of catch basins and then piped to an existing
system to the north, and ultimately to nearby Fanno Creek, mimicking the natural
drainage flow (See Exhibit F— Preliminary Plans, Sheet P500— Preliminary Site Utility
Plan). For a preliminary analysis of existing conditions, downstream conditions, and
post-development conditions— including system capacity— please refer to Exhibit K—
Preliminary Storm Report.
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c. Impact minimization
The proposed stormwater quality treatment and detention facility is designed to comply
with CWS standards, which protect the public at large, public facilities systems, and
effected private property users from potential harm due to concentrations of chemicals,
turbidity, and high runoff flow volumes during storm events. Please refer to the Clean
Water Services Pre-Screening Site Assessment from provided in Exhibit G.
4. Parks System
a. Effect on public facilities and services
The proposed net increase of 9 homes can be anticipated to produce a corresponding
increase in utilization of park facilities and services, based on utilization rates
characteristic of the local area. Some of this impact may be positive, such as higher
participation rates in activities supported by user fees.
b. Improvements to meet City standards
No specific park improvement to meet a City or County standard is called for within the
subject property. The site is not suitable for use as a park facility because of its limited
size and the presence of existing homes.
c. Impact minimization
As future homes are constructed, all applicable Systems Development Charge (SDC) fees
will be collected as building permits are issued. Consistent with the adopted SDC
ordinance authorizing such fees, funds will be expended by the City to provide
appropriate public facilities, including parks. This will minimize potential negative
impacts on the public at large, and on the public parks system.
5. Water System
a. Effect on public facilities and services
The proposed development will produce additional demand for water, consistent with
projected service demands for the area.
b. Improvements to meet City standards
The proposed development will extend 8" public water lines in public streets.
c. Impact minimization
Construction of 8" public water line extensions will provide service at acceptable levels
to the proposed development. As future homes are constructed, all applicable Systems
Development Charge (SDC) fees will be collected at the time building permits are issued.
Consistent with the adopted SDC ordinance authorizing such fees, funds will be
expended by the City to provide appropriate public facilities, including water system
improvements. These fees will minimize potential negative impacts on the public at
large. There is an existing fire hydrant at the northwestern corner of the subject
property.
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6. Sewer System
a. Effect on public facilities and services
The proposed development will produce additional demand for sanitary sewer service,
consistent with projected service demands for the area.
b. Improvements to meet City standards
Clean Water Services provides public sanitary sewer in SW 100th Ave. The subject
property slopes generally east/northeast. The preferred route for making a connection
is to SW 100th Ave. A gravity line will be constructed by the developer along the length
of the proposed Jason Lane, connecting into a manhole at the intersection with SW
100th, and continuing northward in SW 100th Ave. to an existing manhole in the SW
100th right-of-way approximately 400' north of the subject property.
The sanitary sewer main line will consist of an eight-inch (8") pipe gravity system. The
proposed sanitary sewer system is illustrated on Exhibit F— Preliminary Plans, Sheet
P500— Preliminary Utility Plan.
c. Impact minimization
Construction of an 8" sanitary sewer line extension will provide service at acceptable
levels to the proposed development. This is a positive impact on the area because it
implements the City's Sanitary Sewer System Plan at the subject site. These
improvements benefit the public at large by improving the public sanitary sewer system
pursuant to City standards. The subdivision improvements also tie into a planned City
extension of the sewer lines to service properties located to the south of the site,
benefiting the public by reducing public expenditures for this planned improvement.
7. Noise Impacts
a. Effect on public facilities and services
Single-family residential use does not typically produce significant noise impacts.
Rather, it is typically the object of noise protection measures applicable to commercial
and industrial users of land. The proposed development cannot reasonably be expected
to have any significant noise impact on the neighboring area.
b. Improvements to meet City standards
As no noise impacts are anticipated, no noise-related improvements are warranted.
c. Impact minimization
As no noise impacts are anticipated, no noise-related strategies are warranted.
8. Dedication of Real Property Interests
a. Internal, Local Street Rights-of-Way
The Developer will dedicate right-of-way and improve all local internal streets within the
proposed development to meet applicable City design standards.
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b. Stormwater Management Facilities (Easement)
A new water quality and detention facility (Extended Dry Basin) in a tract at the
northeastern corner of the subject property will provide for stormwater management.
9. School System
The City of Tigard Comprehensive Plan contains objectives and policies for school
facilities planning. Schools are considered Public Services and are discussed in Chapter
7, Public Facilities and Services, more particularly Section 7.8-Schools. That Section
notes that both of the school districts that serve Tigard are separate taxing districts and
are not the responsibility of the City of Tigard government. Currently, there is no specific
school capacity formula in the City of Tigard's comprehensive plan or development
code.
Although Tigard-Tualatin School District 23J (TTSD) does not currently meet the state
statutory definition of a "high growth" district, the District prepared a Facility Plan in
2004 for its own planning purposes. A facility plan helps a district inventory its current
district facilities, assess historical and future enrollment trends, evaluate facility
capacity, and plan accordingly for acquisition, re-use, or sale of property for district
facilities. Based on information in that Plan, the Applicant believes that the
development will not negatively impact the school system, because future development
of the property was considered as a part of the school population forecasting
component of the facility plan.
Policy 7.8.1 of the Comprehensive Plan provides that the City shall monitor school
capacity by requiring requests for development proposals and permits to be reviewed
by the applicable school district for effects on school capacity as a pre-condition to
development. In furtherance of that policy, when the City deems the subdivision
application complete, it will submit notice to TTSD (as well as other affected service
providers) for comments.
Summary
This Impact Study demonstrates that the impacts associated with the proposed development
will be either positive - e.g. by furthering implementation of the Tigard Comprehensive Plan - or
will be satisfactorily minimized —e.g. through compliance with applicable City or County
standards or payment of SDC fees. Therefore, the proposed development will not cause any
significant negative impacts on the public at large, public facilities systems or affected private
property owners.
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