HomeMy WebLinkAboutNoise Variance requestPUBLIC WORKS DEPARTMENT
M E M O R A N D U M
DATE:
February12, 2016
TO:
Jennifer Henning
FROM:
Michael Benoit
SUBJECT:
Noise Variance Request
I-405 / SR-167 Direct Connect Sanitary Sewer Relocation
The City of Renton Wastewater Utility is requesting 10 non-consecutive nights of temporary noise variance to complete the relocation of sanitary sewers related to the WSDOT I-405 /
SR-167 Direct Connect project. We are asking for relief from the requirements of the Renton Municipal Code, Title VIII – Health Sanitation – Chapter 7 and Noise Level Regulations,
as per section 8-7-2 and the Washington State Administration Code (WAC) Chapter 173-60, allowing the City’s contractor to work at night. The project is planned to commence May, 2016
and be completed by September, 2017.
Project Narrative:
The project is located south and east of I-405, north of S 15th Street and west of Smithers Avenue S. Washington State Department of Transportation is constructing the I-405 / SR-167
Direct Connector project. As they expand the highway limited access right-of-way south, the public utilities that serve the residential neighborhood in the Talbot Hill area need to
be relocated.
The majority of the utilities will be relocated as part of WSDOT’s design build project. Because of timing issues WSDOT is contracting with the City of Renton to relocate the Sanitary
Sewers under their project. The sanitary sewer needs to be relocated first (because of depth) prior to the relocation of the Olympic Pipeline, which needs to be relocated in order
to clear the way for WSDOT to construct their project.
As part of the sanitary sewer relocation, there will be two portions of the project that will not utilize typical open cut construction practices.
There will be approximately 800 feet of sewer main installed in an east-west direction (from Whitworth to the west) parallel with and along the southern boundary of the I-405 right-of-way
utilizing horizontal directional drilling (HDD). This method was chosen over open cut because the sewer line will be 40’-50’ deep.
There will also be about 240 feet of sewer main installed under I-405 to the north that will be installed by guided pipe ram in lieu of open cutting the highway.
The remaining portions of the sewer relocation will be accomplished by standard open cut method.
Special Circumstances:
Renton is not specifically scheduling to do night work for the sanitary sewer relocation. However, when doing horizontal directional drilling (HDD) as needed for a portion of this project,
“momentum” is everything. Once you have begun a specific task in the process (ie. pulling the pipe), you cannot effectively stop the task and restart. To stop and start a task such
as pulling the pipe would have a high risk of failure in completing said task and would not be considered an acceptable means of construction. To stop the task would create difficulties
and hardship in a couple of ways. First, it is difficult to overcome the inertia and friction to restart the task. Second, undue delay increases the probability of borehole instability
which can add significant installation forces that decrease the probability of pulling in the product pipe successfully.
The plan is and every effort will be made to do the work between the hours of 7:00 am to 10:00 pm. However, during specific tasks related to the HDD (ie. pulling the pipe), if they
run into problems or the work is proceeding slower than anticipated they will have to continue the work until the task is completed, even if that means continuing past 10:00 pm. For
this project, we are having about 800 feet of 12” sewer main installed by HDD. That 800 feet of pipe needs to be pulled into place as one continuous task. It could go in easily and
the task would be completed in a normal working day or they could run into difficulties and the task will continue into the night.
Most of the noise will be confined to the two entry / exit points on either end of the HDD. There will be the need to continually move the “mud” (the material used to lubricate and
cool the drill head, casing and pipe during the processes and stabilize the borehole) from the receiving pit back to the entry pit so the area between the pits would be subject to the
truck noise
Table 1. Equipment Sound Levels (dBA)
Equipment
Sound Level
(dBA) at Source
Approx. Sound
Level (dBA) at
50 feet (dBA)
Approx. Sound
Level (dBA) at
100 feet
Constant or Common Noise Sources
Quiet Drill Rig
104
69
63
Generator
103
68
62
Soil Separation Plant (SSP)
111
76
70
SSP Engine
99
64
58
Excavator/Loader
100
62
56
Dump Truck (Idling)
102
64
58
Mud Pumps (2)
104
69
61
Mud Sump Pump
100
66
60
Short-Term or Intermittent Equipment Noise
Vactor Truck
123
88
82
Proposed Nighttime Noise Mitigation Measures
To limit the potential effect of construction-related noise at the residences near the HDD portal sites, several noise mitigation measures have been considered. The other mitigation
measures listed can be considered part of a best management practice plan.
Constructing a 16-foot tall noise wall around the perimeter of the portal site. The truck/equipment entrance will be placed to face away from houses and would not require a barrier
Give at least 72 hour advance notice to nearby residents of the time periods when particularly noisy work and potential nighttime construction activities (e.g. pullback) will be occurring
through mailers, door hangers, or other similar notification methods.
Create and utilize a noise mitigation training program, which shall be implemented for all field-worker supervisory personnel including sub-contractor supervisors. (Required in construction
contract.)
Take noise level readings. At a minimum, the contractor will be required to take a base noise level reading before the start of construction activities, at the start of the drilling,
and after noise mitigation measures have been installed.
Equip all vehicles with ambient sensitive backup warning devices. The Contractor may use back-up observers in lieu of back-up warning devices for all equipment except dump trucks in
compliance with WAC Chapter 296-155-610 and 296-155-615. The Contractor shall use back-up observers and back-up warning devices for dump trucks in compliance with WAC Chapter 296-155-640.
Alternative Nighttime Noise Mitigation Measures
If the above measures are determined to be insufficient, the following measures may also be implemented in an attempt to reduce the construction noise levels.
Using acoustical blankets, pads, and/or boards to control metal-on-metal clanging noise or other banging noises that can occur while picking up drill pipe and setting on racks; moving
the drill pipe from pipe racks, and making up the drill pipe.
Offer to relocate the nearest residents during nights when construction activities would occur (e.g., during pullback) or during days with particularly noisy daytime activities (e.g.,
casing installation).