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401 S. Jackson St. | Seattle, WA 98104
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To: Clark H. Close, Senior Planner, City of Renton
From: Leyla Karaman, Sound Transit
Prepared by: WSP and Furtado & Associates
Date: September 3, 2021
Re: Noise Variance Request Justification for I-405 BRT Site Investigation
Sound Transit is submitting a Noise Variance Request application for the geotechnical boring and
utility potholing site investigations to complete I-405 BRT project design. As described in the Project
Narrative, the work will exceed the maximum environmental noise levels, per WAC Administrative
Code Sections 173-60-020, between the hours of 10pm and 7am and will require a Variance from the
City of Renton, per Chapter 7 of the Renton Municipal Code (RMC-8-7-8). Below is the response to
each variance factor included in Section D of the code.
D. Factors For Granting Variance: The decision maker, in passing upon an application for a variance,
shall consider all technical evaluations, all relevant factors and standards specified in other
sections of this Chapter, and in addition thereto shall consider the following, none of which is
mandatory for the granting of the variance:
1. That the applicant suffers practical difficulties and unnecessary hardship and the variance is
necessary because of special circumstances applicable to the applicant’s property or project,
and that the strict application of this Chapter will deprive the subject property owner or applicant
of rights and privileges enjoyed by others.
Applicant Response: The WSDOT-approved Traffic Control Plans for the I-405 limited access
right-of-way (including traffic control that impacts limited access right-of-way) require that the
boring and potholing work be performed either between the hours of 10pm to 4am or 8pm to
5am, Sunday – Thursday due to the existing traffic volumes, roadway capacity and geometry,
and WSDOT's safety requirements for the maintenance of operation of the I-405 corridor. See
Attachment 2: Traffic Control Plans.
2. That the granting of the variance will not be materially detrimental to the public health, welfare or
safety, or unduly injurious to the property or improvements in the vicinity of the location for which
this variance is sought.
Applicant Response: Temporary nighttime work, up to two (2) nights, is proposed to minimize
the impact to traffic congestion and safety for all roadway users in the vicinity of the work. While
there are no residences within a 300-foot radius of the boring and potholing work, the Red Lion
Hotel (1 S Grady Way, Renton) has been identified as a Class A receiving property within this
distance. The hotel meets the WAC definition of Class A environmental designation for noise
abatement (EDNA): “Lands where human beings reside and sleep” (WAC 173-60-030).
EXHIBIT 3
RECEIVED
Clark Close 09/03/2021
PLANNING DIVISION
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Project Memorandum
Attachment 1, Neighborhood Detail Map, shows the fieldwork locations and proximity to the
hotel property and structures.
Background noise at the boring/pothole locations within the I-405 limited access right-of-way
and SR 167 right-of-way includes airplane and freeway traffic noise and is approximately 70-80
decibels. The maximum noise levels projected for this work, based on the use of auto sampling
hammer and vacuum truck, are estimated to be 115-120 decibels at the work location,
decreasing with distance to 90-100 decibels at 50-foot distance, and 80-100 decibels at 100-
foot distance (see response to 4b).
The persons residing at the Red Lion Hotel will be impacted to the minimum extent feasible for
a duration of up to two (2) nights and based on the minimal and temporary nature of impacts is
not materially detrimental to public health, welfare or safety, or result in an impact to the
property or other improvements in the vicinity of the location for which the variance is sought.
3. That the variance sought is the minimum variance which will accomplish the desired purpose.
Applicant Response: The Administrative Noise Variance for two (2) nights will allow the
completion of the necessary fieldwork for the project in the minimum number of hours/nights
needed. The potholes will be cored rather than jack hammered to accomplish the work and
minimize the noise impact. See Attachment 1, Neighborhood Detail Map.
4. That the variance contains such conditions deemed to be necessary to limit the impact of the
variance on the residence or property owners impacted by the variance. The variance approval
may be subject to conditions including, but not limited to, the following:
a. Implementation of a noise monitoring program;
Applicant Response: Unless the City determines this condition to be appropriate for the Noise
Variance approval, Sound Transit does not propose to provide a noise monitoring program for
the two nights of work; however, if a complaint is received, work would halt and would proceed
with monitoring if noise attenuation barriers are then installed around the drill site.
b. Maximum noise levels;
Applicant Response: Background noise at the boring/pothole locations within the I-405 limited
access right-of-way and SR 167 right-of-way includes airplane and freeway traffic noise and is
approximately 70-80 decibels. The maximum noise levels projected for the pavement boring
work, based on the use of auto sampling hammer, is estimated to be 115-120 decibels at the
work location, decreasing with distance to 90-100 decibels at 50-foot distance, and 80-100
decibels at 100-foot distance.
The maximum noise levels projected for the utility potholing work, based on the use of the
vacuum truck, is estimated to be 70-80 decibels at the work location, decreasing with distance
to 60-70 decibels at 50-foot distance, and 55-63 decibels at 100-foot distance (see Figure 1).
DocuSign Envelope ID: 2E231420-43C5-495E-9C18-380F6EB76097
Project Memorandum
These estimates are conservatively high and are based on limited data obtained from simplified
monitoring of noise levels in the vicinity of drilling operations in urban environments. In any
case, noise levels (sound pressure levels) attenuate in general accordance with an inverse
square law when considered to be emanating from a point source (i.e. drill rig). An example,
simplified attenuation curve for a point source with a sound pressure level of 110 dB(A)
measured at 5 feet from the source is shown in Figure 2 below.
Figure 1: Vacuum Truck Noise Levels by Distance (in Feet)
Note: Sound levels taken in open air space for Tellus Vacuum Truck back motor John Deere 4046 Final Tier
4 Engine
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Figure 2: Sound Attenuation Curve for a Point Source by Distance (in Feet)
Note: Sound attenuation curve example is for sound pressure level of 110 dB(A) measured at 5 feet
c. Limitation on types of equipment and use of particular equipment;
Applicant Response: Fieldwork equipment will include a truck-mounted drill rig (i.e. CME-75)
for mud-rotary drilling, a truck-mounted direct-push rig (i.e. Geoprobe 7800) for geoprobe
sampling, and a core drill and vacuum truck for potholing. See Attachment 3 Equipment List.
d. Limitation on back-up beepers for equipment;
Applicant Response: Back up beepers for equipment will operate per OSHA and L&I rules and
regulations in the WAC and RCW.
e. Required use of noise shields or barriers;
Applicant Response: Mitigation Measures listed in the Project Narrative include:
If a complaint is received, work will halt. Work may proceed, with monitoring, if noise attenuation
barriers are then installed around the drill site.
Sound Pressure Measured at 5 ft from Point Source = 110 dB(A)
60.0
70.0
80.0
90.0
100.0
110.0
120.0
0 50 100 150 200 250 300 350 400 450 500Sound Pressure (dB[A])Distance from Source (ft)
Sound Pressure Attenuation Curve
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f. Restrictions to specific times and days;
Applicant Response: Fieldwork will occur over two (2) consecutive nights between the hours
of 8pm to 5am, or 10pm to 4am, Sunday – Thursday as per the approved TCP included in
Attachment 2.
g. Specific requirements for documentation of compliance with the noise variance conditions;
Applicant Response: Sound Transit will document compliance with the noise variance
conditions per the approved Administrative Noise Variance Request.
h. Specific requirements for notification to nearby residents;
Applicant Response: Notification of residents, by mail, within 300 feet of the sites ten (10)
days prior to the night work commencement. This notification will include the type of work, as
well as phone number or email to request more information including specific requests or
concerns as well to file complaints during activities.
i. Required cash security to pay for inspection services to verify compliance;
Applicant Response: Sound Transit does not propose to provide cash security to pay for
inspection services to verify compliance unless the City determines this condition to be
appropriate for the Noise Variance approval.
j. Required access to the project by the City to verify compliance with the noise variance
conditions;
Applicant Response: Access to the work zone will require that City personnel wear
appropriate PPE, including a hard hat, reflective vest, steel-toed boots, eye protection and
hearing protection. City personnel may enter the work zone when they have gained the
attention and invite of the person in responsible charge of the drilling crew.
k. Specific program to allow for temporary hotel vouchers to effected residents;
Applicant Response: No residential properties are within 300 feet of the site investigation work
in the right-of-way. See Mitigation Measures included in the Noise Variance Project Narrative for
those measures included to minimize noise impacts to the hotel property within 300 feet of the
work.
l. Requirements for written verification that all workers understand the noise variance conditions
for the project; and
Applicant Response: See Mitigation Measures included in the Noise Variance Project
Narrative. All fieldwork personnel will be de-briefed on the conditions under which the variance
is granted and the approve Noise Variance Request will remain on-site while the work is
performed.
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m. Provision allowing the City to immediately revoke the variance approval if the variance
conditions are violated.
Applicant Response: This provision is expected to be included in the final decision issued by
the City of Renton.
5. The importance of the services provided by the facility creating the noise and the other impacts
caused to the public safety, health and welfare balanced against the harm to be suffered by
residents or property owners receiving the increased noise permitted under this variance.
Applicant Response: The noise impacts resulting from the limited site investigations for the I-
405 BRT project are minimal and temporary in nature. The I-405 BRT project will ultimately
provide frequent and reliable high capacity transit service to the region and would benefit the
Red Lion hotel patrons located across the street from the future South Renton Transit Center.
6. The availability of practicable alternative locations or methods for the proposed use which will
generate the noise.
Applicant Response: Pavement boring and utility pothole site investigations are required to
inform roadway improvement design associated with the I-405 BRT project at these specific site
locations.
7. The extent by which the prescribed noise limitations will be exceeded by the variance and the
extent and duration of the variance.
Applicant Response: The maximum noise levels projected for this work, based on the use of
auto sampling hammer for pavement boring work, and vacuum truck, are estimated to be 115-
120 decibels at the work location, decreasing with distance to 90-100 decibels at 50-foot
distance, and 80-100 decibels at 100-foot distance (see response to 4b above). Per the WAC
173-60-040, maximum permissible environmental noise levels, the noise limitations for a Class
A EDNA receiving property (hotel) from a Class C source (right-of-way) is 60 dBA. Between the
hours of 10:00pm and 7:00am, the noise limitations are further reduced by 10 dBA for Class A
EDNA receiving properties; therefore, the permissible noise level of 50dBA would be exceeded
by the maximum noise level estimates projected for the site investigation work for a limited
period. The Noise Variance Request is for a total of two (2) nights to complete two (2) pavement
borings and six (6) utility potholes.
DocuSign Envelope ID: 2E231420-43C5-495E-9C18-380F6EB76097
Project Memorandum
DocuSign Envelope ID: 2E231420-43C5-495E-9C18-380F6EB76097