HomeMy WebLinkAbout2024-05-06 Council presentation Item ciTv of Y. Y 6, 2024
Date: Monday, May TWIN f'AI.1{s
To: Honorable Mayor and City Council
From: Nathan Erickson, Environmental Manager
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PRESENTATION
Request:
Spring 2024 odor study update
Time Estimate:
The staff presentation will take approximately 5-10 minutes.
Background:
The City of Twin Falls has spent several years studying the impacts and sources of hydrogen sulfide gas,
which has caused citizens to be concerned about odors. In the past year, the council has approved
funding for a second odor scrubber to be used this summer to help mitigate citizens' concerns. The
council has also funded the purchase of sensors that measure hydrogen sulfide concentrations in
wastewater flows.
For the summer of 2024, the city has prepared a plan to continue the odor study in the Grandview North
area to better understand the options available for installing a permanent carbon-based odor scrubber
(see attached 2024 Grandview North Odor Study). As part of this study, the city has scheduled an open
house on May 9, 2024, from 6:00 to 8:00 p.m., inviting community members to share their thoughts and
answer any questions about this summer's odor study.
The city has also begun to see results from using the new hydrogen sulfide sensors and will share some
initial results during the presentation.
Approval Process:
N/A
Budget Impact:
Regulatory Impact:
N/A
History:
N/A
Analysis:
N/A
Conclusion:
With support from the city council, progress is being made to identify ways to address hydrogen sulfide
sources and tools for mitigation. Public awareness and involvement from citizens and the city council
have been critical to the ongoing success of this project.
Attachments;
1. 2024 Grandview North Odor Study
CITY OF CITY OF TWIN FALLS
TWIN FALLS Public Works Department
119 South Park Avenue West
Twin Falls, ID 83301
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2024 North Grandview Odor Study
Background
The City of Twin Falls City Council continues to support the ongoing study of sources and ways
to mitigate foul odors throughout the City of Twin Falls. The main culprit has been tied to hydrogen
sulfide,which, in some locations,is dispersed in the community through the sewer system.The city has
collaborated for many years with an engineering firm to study the source of these odors and find ways to
eliminate the sources or mitigate the impact on citizens.In the spring of 2023,the city purchased a
carbon-based odor control system for testing the mitigation of hydrogen sulfide gases from the sewer
system. The results were positive,and in December of 2023,the City Council approved purchasing a
second carbon-based odor control system to continue the study and help mitigate hydrogen sulfide in two
areas within the City that need it most during the summer of 2024.
Mobile odor scrubber
In 2023,the City of Twin Falls purchased a trailer-mounted carbon-based odor control system
(mobile odor scrubber)from Anua International. The mobile odor scrubber can pull up to 650 cubic feet
per minute of air through a 10-inch flexible hose connected to a sewer manhole. The air pulled from the
sewer is pushed through approximately 35 cubic feet of activated carbon pellets. The carbon pellets
absorb odorous hydrogen sulfide from the sewer. The mobile odor scrubber is intended to be used to
better understand the permanent options available to address foul odors from the sewer that impact the
community.
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Purpose of project
During the summer of 2024,the City of Twin Falls plans to utilize the mobile odor scrubber to
test locations for hydrogen sulfide mitigation from the Grandview sewer trunk line. This will be done by
placing the mobile odor scrubber at different locations in the community north of Pole Line Road along
the Grandview sewer trunk line. The goal is to understand the odor scrubber's effectiveness and identify a
proposed location for a permanent installation of a carbon-based odor scrubber.
Possible locations
City staff have evaluated the study area for possible locations to test the mobile odor scrubber.
Attachment A has the locations evaluated, along with an analysis of the location based on the criteria for
selecting a location.The criteria considered when assessing locations were:
• Would the manhole used impede the flow of traffic?
• Is a city-owned power source(120v)available within 200 ft?
• Is the location feasible to be used as a test location?
• Does the area in proximity provide feasible options for a permanent location?
Additionally,Appendix B identifies the location of odor loggers used to document and better understand
the concentration of hydrogen sulfide within the sewer.
Public involvement
As the City of Twin Falls has grown, citizens have had ongoing concerns regarding the odors in
the proposed study area. The City is committed to working with the community to find long-term
solutions to the odor problem. Citizens are encouraged to report odor concerns via the online odor report
form on the City of Twin Falls homepage.Additionally,citizens are encouraged to provide feedback
throughout the study to help City staff identify the best path forward for the entire community. To
facilitate this process,the City will hold the following meetings open to the public:
• Project kickoff Open House—May 9, 2024,4-6 pm City Council Overflow Room at City Hall.
The meeting is open to the public to provide information,answer questions, and for City staff to
receive feedback from the public. The odor Scrubber will be on site for the public to see.
• End of summer update Open House—September 24,2024,4-6 pm, City Council Overflow
Room at City Hall. City staff will provide data collected and what has been learned from the data.
They will also discuss the current status of the project to receive feedback from the public.
• Results of the 2024 study Presentation to Council—October 28,2024, 5 pm,Council
Chambers at City Hall.Presentation of results and recommendations to the City council.
Questions
If you have any questions or would like to provide feedback,please contact:
Nathan Erickson
(208)735-7272
nerickson@tfid.org
Appendix A: Locations explored for testing mobile air scrubber.
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An analysis of each location was considered for testing the mobile air scrubber.
Site A(B2-59)—Manhole B2-59 is located approximately 30 feet east of the Grandview trunkline
in the middle of the sidewalk on the north side of Pole Line Road.Due to its location on the
sidewalk,its use would impede pedestrian passage and ADA compliance; it is also in ITD's right
of way,which would likely make it challenging to acquire an easement.This is not likely a viable
option for a test or permanent location.
Site B(B2-290)—Manhole 132-290 is in the Grandview trunkline. located within the paved road
on the east edge. There is a City-owned pressurized irrigation pump station located approximately
200 feet to the north,which could provide power.Due to the location of the manhole on the edge
of the road,traffic would likely be impacted, and traffic may be reduced to one lane during the
test. It is likely not the best location for a test due to traffic impact;however,the location of the PI
station offers some potential for a permanent location.
Site C(B 1-1 95)--Manhole B1-195 is located approximately 170 feet east of the Grandview
trunkline through an 8-inch sewer line and is in the grass in a park/stormwater retention area
owned by the City. There is a sprinkler control box approximately 70 feet to the southwest,which
could possibly provide power. For the test,this location appears promising. It also has the
potential for a permanent location.
Site D(B 1-1 70)—Manhole B1-170 is located approximately 230 feet south of the Grandview
trunkline through an 8-inch sewer line and is in the center of a cul-de-sac. Though this location
would have minimal traffic, its position in the center of the cul-de-sac is not ideal.Additionally,
no city power source is nearby, and the stormwater basins to the north are deep and not owned by
the City. This is likely not a viable option for a test or permanent location.
Site E(B 1-1 09)—Manhole B1-190 is located approximately 30 feet south of Grandview trunkline
on Columbia Drive through an 8-inch sewer line.Due to the manhole's location on the road,
traffic would likely be impacted. Additionally,there is no city power source nearby and no
property owned by the City. This is likely not a viable option for a test or permanent location.
Site F(B1-48)—Manhole B1-48 is located approximately 250 feet south of the Grandview
trunkline on the east edge of Park View Drive through an 8-inch sewer line. The manhole is on
the edge of the road,which is likely wide enough that traffic could be directed around it and keep
both lanes open. The closest city power appears to be approximately 275 feet to the northeast.
The distance from city power is more than 200 feet,which is necessary for this test;however,if
power could be figured out,this may be a possible test location. The City owns the park to the
east of this manhole,and the park/stormwater area could be a viable option for a permanent
location.
Site G(B1-29)—Manhole B1-29 is the last manhole in the Grandview trunkline before it drops
off the canyon rim to the wastewater treatment plant. The manhole is located on the canyon rim
walking path.A section of the walking path would need to be closed during the test,but users
could be redirected around the area via a different path. City power is approximately 150 feet to
the west. For the test,this location appears promising. The City owns the park to the west,and the
park/stormwater area could be a viable option for a permanent location.
Appendix B: Locations of hydrogen sulfide data logger locations during the test.
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