HomeMy WebLinkAboutCorrespondence ENG 1/22/2004
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Brari~~ Engineering1anner: I 0 f I Lf p~
February 4, 1998
Project No. 91-187
310 5th Street
Springfield, Oregon 97477
(541J 746-0637
Fax (541J 746-0389
City of Springfield
Development Services Department
225 5th Street
Springfield, Oregon 97477
Re: Staff Report and Findings for MountainGate Development Company
Branch Engineering has reviewed the subject staff report and would like to respond to four staff
conditions:
1. Access driveways to MountainGate Drive between Aster and Dogwood.
The Master Plan, as submitted, anticipated six driveways along the subject section of
MountainGate Drive. City staff's position is that no driveways should be allowed along this
section of MountainGate Drive.
I have reviewed the lot layout and configuration in the vicinity of subject section of Mountain Gate
Drive and propose to revise the configuration to reduce the number of driveways. By accessing
most lots from alternative public streets, the number of driveways along subject section of
MountainGate Drive would'be reduced from six to one. Topographic constraints restrict access
from three lots to alternative public streets; therefore, these three lots would be served by the one
proposed driveway onto MountainGate Drive.
Attached are supporting calculations demonstrating that the required sight and safe stopping
distances for motorists turning right or left from the proposed driveway are met within the
available distances. Therefore, we request that one driveway, as shown, be permitted along the
subject section of Mountain Gate Drive.
2. Variance to Street Widths
The applicant will accept staff's proposal for a 32' wide street for the southerly section of
MountainGate Drive.
However, the applicant continues to request a variance to the street width from 36' to 28' for the
north section of Mountain Gate Drive. The primary reasons for this request is the existing
steepness of the slope and the anticipated difficulty in construction due to the presence ofrock
TRANSPORTATION
CIVIL
SURVEYING
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near the surface. Additional factors that should be considered in this request include:
A)
B)
D)
E)
the applicant has modified the lot layout along this section of MountainGate Drive
as shown on the attached figure "Revised Access Plan" to reduce the number of
driveways from six to. one, ,. c/o l'O'~
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left turn lanes would not be needed along this roadway section, --
C)
on street parking would not be permitted along this section allowing wider travel
lanes to accommodate both auto and bike traffic.
the vertical curves that are proposed along this section are minor and would have
no appreciable impact to traffic operations.
transition from a 36' wide street to a 28' wide street near Aster and Dogwood
Streets could be easily accomplished. Each curb line would narrow 4' in about 50'
to 100'. Gradual street width transitions on horizontal curves are not uncommon
and to my knowledge do not present a hazardous condition.
The above factors in response to staff concerns coupled with those submitted in original request
provide the basis for this request.
3. Storm Sewer Condition - #2
City staff has requested that a storm sewer lateral be provided to each lot and that no roof,
foundation, or surface runoff, or subsurface flow be directed to the gutter (Condition #2).
It is my opinion, as welJ as that of other design professionals with considerable experience in
performing civil engineering in the hillside areas of Springfield and Eugene over the past 20-30
years, that directing lot, roof, and fo'undation drainage to properly designed concrete curb and
gutter sections is a time tested and accepted means of handling storm drainage. Methods exist to
calculate lot drainage volume and to determine gutter flow widths and volume. With proper
. street/gutter design and inlet design and spacing, the gutter flow has been and is an integral part of
the storm draina~e system of most street systems throughout urban areas. '
Some advantages of using gutters for conducting lot drainage to catch basins/inlets include:
I. the gutter is constructed of concrete, the same material used in storm pipe and should
have a similar useful life span,
2. the gutter is easier to maintain or replace because it is at the surface instead of five to ten
feet deep,
3. it is cost effective,
4. it reduces the amount of pipe that otherwise would be installed and require maintenance,
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5. flexibility in design of gutters provides the opportunity for increased flow capacity such as
by increasing the width of the gutter bar and/or by using a parabolic crown street design.
In summary, extension oflaterals to some lots or areas in MountainOate will be needed to collect
identified spring flow, minor and major drainage flows, etc. However, general use ofthe curb and
gutter section for conveyance of both lot and street water should continue to be permitted. .
4. Ground Water Control- Condition #3
The City staff has requested that a longitudinal drainage system be installed along the uphill side
of all streets constructed on cut slopes. The primary purpose of this system is to protect the street
from intrusion of ground water.
The proposal submitted by the applicant to control ground water includes installation of
foundation drains and "wing" french drains in conjunction with house construction on the uphill
side of the street to intercept ground water and direct it to the gutter along with roof storm water.
Further, a geotechnical engineer will perform site investigations and prepare a detailed report on a
phase by phase basis identifying particular requirements needed for each phase. He will also be
present during street and trench excavation and make recommendations and plan changes to
accommodate site specific conditions that may arise.
Other precautions that will be taken include:
a. . installation of french drains to dewater the trenches and direct the water to the
storm collection system. This would include dewatering of sanitary and utility
trenches.
b. road fills will be designed, inspected and tested to ensure proper placement and
compaction.
In summary, we believe that the applicant's plan which includes a lot drainage collection system
coupled with a site-specific approach to dealing with ground water conditions during construction
and applying the appropriate subdrainage measure is consistent with good engineering practice.
Further, we believe that utility trenches located on the uphill side of the street (as preferred by the
utility company) ~oupled with trench drain connections to the storm sewer system v.:i11 provide
another means of intercepting ground water. Further, we believe the storm sewer and sanitary
sewer trenches with trench drains to the storm sewer will provide additional protection for the
road base. If the hearings officer decides that a longitudinal french drain is needed, we request
that alternatives such as illustrated in the ORl submittal be strongly considered.
If you have any questions, please give me a call.
Respectfully submitted,
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PROPOSED ACCESS PLAN
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REVISED ACCESS PLAN
2/4/98
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Masood Mirza
City of Springfield
225 5th Street
Springfield, Oregon 97477
Re: Access to Mountaingate Drive between Aster and Dogwood Streets
Dear Masood,
At the request of the City, access to Mountaingate Drive is to be prohibited between
Aster and Dogwood Streets. We have researched this issue and found we can comply
with this request with the exception of one access point. This point will serve three lots,
as shown in the attached figure, which cannot be served from Dogwood due to slope
restrictions.
The proposed access is a shared pan-handle driveway which conforms to the
Springfield Development Code for minimum separation between a standard driveway
and the nearest intersection (Table 32-4). The proposed access is located within a
12% grade on Mountaingate Drive which also meets City requirements.
The proposed access was further evaluated for adequate sight distance. The following
summarizes the sight distance calculations which are included with this letter.
Mountaingate Drive is a proposed collector street with a design speed of 30 MPH. It is
anticipated the curvature of Mountaingate Drive and the 12% grade through the access
area will produce lower running speeds; however, a design speed of 30 MPH was used
for sight distan6e calculations.
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The required sight distance for vehicles turning right (downhill) is 251', and for vehicles
turning left (uphill) is 712'. The total sight distance provided for vehicles turning right
(looking left) is 305' and for vehicles turning left (looking right) is in excess of 1000'
(this sight distance is unobstructed with the exception at] Ir",,,,'>..) The stopping sight
distance for vehicles traveling on MountaingateDrive is 240' with 12% down grade and
174' with 12% up grade.
Please review this information and if you have any questions or concerns please do not
hesitate to call.
Sincerely,
Chris M. Clemow, P.E.
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Date:
To:
From:
Subject:
February 22, 2002
City of Springfield
~12- ~ FT
Memorandum
Jim Donovan, Planner II
Gary McKenney, P.E., Transportation Planning Engineer
MountainGate Subdivision Phase 1, Journal No. 2001-04-0087
The Transportation Division has reviewed the materials provided with the subject application.
Please include the following Findings and Conditions in the final decision package.
General
Findings
Finding: The land area involved with this application is within the boundary of the MountainGate
development Master Plan.
On June 22, 1995 the Springfield Development Services Department issued a decision requesting
the applicant to make revisions to the Master Plan for submittal to the Hearings Officer.
On May 13-15, 1998 the Springfield Hearings Officer issued the following land-use decisions
regarding the Master Plan and associated variance requests, which are pertinent to the
transportation issues in this application:
I) Conditional approval of the Master Plan (Journal No. 95-02-39),
2) Conditional approval of a variance request to allow a paved width of 28 feet for portions
of MountainGate Drive, and to allow a 60-foot right-of-way width for MountainGate
Drive and Dogwood Street (Journal No. 97-05-124), and
3) Conditional approval of a variance request to the requirements of section 26.060(2)(a-c)
ofthe Springfield Development Code (SDC) concerning maximum street and driveway
grades (Journal No. 97-05-125).
Thus, criteria of approval for the proposed subdivision include all applicable SDC criteria as
modified and/or supplemented by conditions established in the above noted decisions.
Finding: As part of the Master Plan approval process the applicant submitted a Traffic Impact
Study (TIS), which was based on assumptions about the type, intensity and timing of
developments that could reasonably be anticipated on the site. The TIS assumed land comprising
the subdivision would be developed as single-family housing as proposed. Based on ITE Land
Use Code 210 (Single-Family Detached Housing) trip generation from this subdivision is
estimated to be as follows:
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. Average Weekday = 43 dwelling units x 9.57 trips per dwelling units = 412 trips
. PM Peak Hour = 43 dwelling units x 1.01 trips per dwelling units = 43 trips
In addition, the assumed development would generate pedestrian and bicycle trips. According to
the "Household" survey done by LCOG in 1994, 12.6 percent of household trips are made by
bicycle or walking and 1.8 percent are by transit bus. These trips may have their origin or
destination at a variety of land uses, including this use. Pedestrian and bicycle trips create the
need for sidewalks, pedestrian crossing signals, crosswalks, bicycle parking and bicycle lanes.
Subdivision Access and Circulation
Findings
1) Finding: Construction activities associated with development and use of the subdivision
will generate vehicle trips and non-motorized trips to and from the site, which require
safe and efficient facilities for access and circulation.
2) Finding: The proposed subdivision will not have safe and efficient pedestrian, bicycle and
vehicular access unless and until the necessary street improvements identified in the
MountainGate Master Plan approval decisions and following conditions are constructed
to city standards and accepted by the Springfield City Council.
3) Finding: Installation of driveways on a street increases the number of traffic conflict
points. The greater number of conflict points increases the probability of traffic crashes.
Effective ways to reduce the probability of traffic crashes include: reducing the number of
driveways, increasing distances between intersections and driveways and establishing
adequate vision clearance where driveways intersect streets. Each of these techniques
permits a longer, less cluttered sight distance for the motorist, reduces the number and
difficulty of decisions drivers must make, and contributes to increased traffic safety.
4) Finding: SDC 32.080(1)(a) stipulates that each parcel is entitled to "an approved access
to!! public street."
5) Finding: Access to subdivision lots are proposed via driveways onto MountainGate Drive
or other subdivision streets.
6) Finding: Access to Lots 2, 3, 4 and 5 is proposed via an 18-foot wide panhandle driveway
over a 20-foot wide shared Private Access Easement.
7) Finding: Access to Lot 39 is proposed via a IS-foot wide panhandle. SDC 16.030 (3) (b) :k.
specifies that single panhandles serving single-family dwellings shall have a minimum of I
20 feet of frontage. .,
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8) Finding: Access to lots 41, 42, and 43 is proposed via a shared panhandle driveway
located near the midpoint of the curve on MountainGate Drive between Aster Street and
Dogwood Street This location is not consistent with the Revised Access Plan (2/4/98)
attached to the February 4, 1998 letter from Jim Branch to the City of Springfield, which
was referenced in Finding 4 of the Springfield Hearings Official's conditional approval of
the Variance requested under Journal No, 97-05-124,
9) Finding: As proposed, bicycle trips on MountainGate Drive would be accommodated in
travel lanes shared with other vehicular traffic,
10) Finding: At the time of Master Plan approval the Hearings Officer noted that Policy 17 in
the Eugene-Springfield Area Transportation Plan (TransPlan) called for on-street bike
lanes to be included "in construction or reconstruction of arterial and collector streets,
unless bike facilities are determined to be unnecessary." In consideritlg a request to
narrow MountainGate Drive to 28 feet for a short distance the Hearings Officer
concluded that the narrowest section should be not less than 32-feet wide to allow for at
least one on-street bike lane, and that no parking should be allowed through the narrowed
section,
11)Finding: As proposed, the width of MountainGate Drive narrows to 32 feet and climbs at
a IS-percent grand for approximately 125 feet in the section south of Aster Street
Immediately south of that section the street curves sharply (lSD-foot centerline radius)
while ascending an II-percent grade, These conditions will restrict sight distances and
slow southbound bicyclists to very low speeds through the section,
12) Finding: The current adopted TransPlan calls for MountainGate Drive to be a signed
bicycle route through the subdivision (Project #84),
13) Finding: To provide for safe and efficient travel by bicycle and other vehicular traffic, a
four-foot wide bicycle lane is required to serve southbound (uphill) traffic along the west
side of MountainGate Drive between Aster Street and the west line of Lot 6,
14) Finding: As designed the proposed subdivision does not provide adequate right-of-way
for traffic signal poles and other appurtenances necessary for the required traffic signal
installation at the intersection of Mountain Gate Drive and Main Street
Conditions of Approval
1) Condition: All public street improvements shall include curb, gutter, roadway pavement,
streetlights, signs, pavement markings, sidewalks, trees, and meet SDC criteria as
modified and/or supplemented by conditions established in decisions approving the
MountainGate Master Plan,
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2) Condition: The design and construction of subdivision improvements shall meet all
applicable conditions of the Springfield Hearings Official's conditional approval of the
Variance to allow a paved width of28 feet for portions of Mountain Gate Drive, and to
allow a 60-foot right-of-way width for MountainGate Drive and Dogwood Street.
3) Condition: The design and construction of subdivision improvements shall meet all
applicable conditions of the Springfield Hearings Official's conditional approval of the
Variance to the requirements of section 26.060(2)(a-c) of the Springfield Development
Code concerning maximum street and driveway grades.
4) Condition: The Private Access Easement shared by subdivision Lots 2, 3, 4 and 5 shall be
sized and designed to allow the safe passage of an AASHTO Single Unit Truck (SU)
vehicle. I
5) Condition: Execute and record ajoint-use access and maintenance agreement over the
Private Access Easement shared by subdivision Lots 2, 3, 4 and 5.
6) Condition: Provide a minimum of20 feet of panhandle lot frontage on Lot 39.
7) Condition: Unless approved through a variance request, access to Lots 41, 42, and 43
must be made consistent with the Revised Access Plan (2/4/98) attached to the February
4, 1998 letter from Jim Branch to the City of Springfield, which was referenced in
Finding 4 ofthe Springfield Hearings Official's conditional approval of the variance
requested under Journal No. 97-05-124.
8) Condition: The design for MountainGate drive shall include a four-foot wide bicycle lane
along the west side to serve southbound (uphill) traffic between Aster Street and the west
line of Lot 6.
9) Condition: Dedicate 25-foot triangular pieces of right-of-way at the corners of
MountainGate Drive and Main Street to accommodate future traffic signal facilities.
10) Condition: Maintain 25-foot triangular vision clearance areas at street intersections per
SDC 32.070.
Please provide a copy of the draft decision for my review prior to issuing thefinal decision.
1 A POLICY ON GEOMETRIC DESIGN OF HIGHWAYS AND STREETS 2001, FOURTH EDITION,
Exhibit 2-2, AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION
OFFICIALS
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