12-09-24 Work Session Agenda and MaterialsCITY COUNCIL
KCITY OF WORK SESSION AGENDA
ALISPELL December 9, 2024, at 7:00 p.m.
City Hall Council Chambers, 201 First Avenue East
See the bottom of the agenda to learn how to provide public comment
and watch meetings live or later.
A. CALL TO ORDER
B. ROLL CALL
C. DISCUSSION
1. Advanced Wastewater Treatment Plant Biosolids Treatment and Disposal
Alternatives Review
D. PUBLIC COMMENT
Persons wishing to address the council are asked to do so at this time. See the bottom of
the agenda to learn the protocol for providing comment.
E. CITY MANAGER, COUNCIL, AND MAYOR REPORTS
F. ADJOURNMENT
SIDEWALK AND TRAILS ASSESSMENT DISTRICT SUB -COMMITTEE
MEETING AGENDA
December 9, 2024, Immediately Following 7 pm Meeting
First Floor Conference Room, 201 First Avenue East
The Sub -Committee meeting will not be available via zoom
and will not be televised or video recorded.
A. CALL TO ORDER
B. APPROVAL OF MINUTES — October 21, 2024
C. DISCUSSION
1. Review of Funding Allocation Model
C. PUBLIC COMMENT
D. ADJOURNMENT
Page 1 of 3
Kalispell City Council Agenda, December 9, 2024
UPCOMING SCHEDULE
Next Regular Meeting — December 16, 2024, at 7:00 p.m. — Council Chambers
City Offices Closed — Wednesday, December 25, 2024 — Christmas Holiday
City Offices Closed — Wednesday, January 1, 2025 — New Year's Holiday
Next Work Session — January 13, 2025, at 7:00 p.m. — Council Chambers
PARTICIPATION
When addressing council please give your name and address, see the last page of the agenda for
the proper manner of addressing the council, and limit comments to three minutes. Comments
can also be emailed to publiccomment2kalispell.com.
To provide public comment live, remotely, join the video conference through zoom at:
hiips://us02web.zoom.us/webinar/register/WN_5ECW1msGQ_Cnz0USQ9jSvw. The Sub -
Committee meeting will not be available via zoom and will not be televised or video
recorded. Raise your virtual hand to indicate you want to provide comment. Due to occasional
technical difficulties, the most reliable way to participate is through in -person attendance.
Electronic means are not guaranteed.
Watch City Council meetings live with the agenda and documents or later with time stamped
minutes at: htt2s://www.kalispell.com/480/Meeting-Videos or live or later on YouTube at:
hllps://www.youtube.com/gcilyofkalispellmontana9632/streams. ofkalispellmontana9632/streams. The Sub -Committee meeting
will not be televised or video recorded.
The City does not discriminate on the basis of disability in its programs, services, activities, and
employment practices. Auxiliary aids are available. For questions about disability
accommodation please contact the City Clerk at 406-758-7756.
Page 2 of 3
Kalispell City Council Agenda, December 9, 2024
ADMINISTRATIVE CODE
Adopted July 1, 1991
Section 2-20 Manner of Addressing Council
a. Each person not a Council member shall address the Council, at the time designated in the agenda
or as directed by the Council, by stepping to the podium or microphone, giving that person's
name and address in an audible tone of voice for the record, and unless further time is granted by
the Council, shall limit the address to the Council to three minutes.
b. All remarks shall be addressed to the Council as a body and not to any member of the Council or
Staff.
C. No person, other than the Council and the person having the floor, shall be permitted to enter into
any discussion either directly or through a member of the Council, without the permission of the
Presiding Officer.
d. No question shall be asked of individuals except through the Presiding Officer.
PRINCIPLES FOR CIVIL DIALOGUE
Adopted by Resolution 5180 on February 5, 2007
■ We provide a safe environment where individual perspectives are respected, heard, and
acknowledged.
■ We are responsible for respectful and courteous dialogue and participation.
■ We respect diverse opinions as a means to find solutions based on common ground.
■ We encourage and value broad community participation.
■ We encourage creative approaches to engage in public participation.
■ We value informed decision -making and take personal responsibility to educate and be educated.
■ We believe that respectful public dialogue fosters healthy community relationships, understanding
and problem solving.
■ We acknowledge, consider and respect the natural tensions created by collaboration, change, and
transition.
■ We follow the rules & guidelines established for each meeting.
Page 3 of 3
c1 Yy (W
KALISPELL
To: Doug Russell, City Manager
From: Susie Turner, Public Works Director
Re: AWWTP Biosolids Treatment and Disposal Alternatives Review
Meeting Date: December 9, 2024
Attachment: Draft Preliminary Engineering Report AWWTP Biosolids Treatment and
Disposal Alternatives Review
Background:
The City is actively reviewing alternatives for the treatment and disposal of biosolids generated
as part of the wastewater treatment process. Currently, the biosolids are primarily disposed of
through composting at Glacier Gold LLC and secondarily through landfill disposal at the
Flathead County Landfill. AE2S, the project consultant, has been engaged to perform the
preliminary engineering report (PER), support project alternative selection, and oversee design
and construction.
The goal of the alternatives review and final project selection is to develop a sustainable, long-
term strategy for managing biosolids while meeting regulatory requirements and minimizing
environmental impacts.
Meeting Discussion:
During this work session, staff and AE2S consultants will present information developed as part
of the PER. The review will include:
• Project Need:
o Glacier Gold Composting changes
o Anticipated regulatory landscape
o Landfill disposal opportunities
• Alternatives Analysis:
o Five (5) alternatives evaluated
o Kepner-TregoeTM Decision -Making Tool
• Monetary and non -monetary factors considered
• Recommendations and Next Steps
• Summary and Questions
Upon reviewing the PER, staff will seek direction from the Council on the preferred alternative
to support the next steps for completion of the PER and project implementation.
City of Kalispell
KCITY OF AWWTP Biosolids Treatment & Disposal
ALISPELL preliminary Engineering Report
KALISPELL ADVANCED WASTEWATER TREATMENT PLANT (AWWTP) BIOSOLIDs TREATMENT &
DISPOSAL PRELIMINARY ENGINEERING REPORT (PER) - DRAFT
Date: December 2024
Prepared By: Advanced Engineering and Environmental Services, LLC (AE2S)
Table of Contents
0.0 Executive Summary .............................................
0.1 Purpose............................................................
0.2 Alternatives Considered ..................................
0.3 Project Costs ....................................................
1.0 Project Planning ..................................................
1.1 Location...........................................................
1.2 Environmental Resources Present ..................
1.2.1 Soils and Geology .....................................
1.2.2 Air Quality ................................................
1.2.3 Surface Waters .........................................
1.2.4 Floodplains...............................................
1.2.5 Wetlands ..................................................
1.2.6 Wildlife .....................................................
1.2.7 Agency Notifications ................................
1.2.8 Human Environment ................................
1.2.9 Environmental Checklist ..........................
1.3 Population Trends ...........................................
1.3.1 Historic Population Trends ......................
1.3.2 Population Projections .............................
1.4 Community Engagement .................................
2.0 Existing Facilities .................................................
2.1 Location Map ...................................................
2.2 History.............................................................
2.2.1 Historic Regulations and Compliance ......
2.3 Condition of Existing Facilities .........................
2.4 Financial Status of any Existing Facilities ........
2.5 Water/Energy/Waste Audits ...........................
3.0 Need for Project ..................................................
3.1 Health, Sanitation and Security .......................
3.2 Aging Infrastructure ........................................
3.3 Reasonable Growth .........................................
4.0 Alternatives Considered ......................................
4.1 Design Criteria .................................................
......................................................................... 6
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PRELIMINARY ENGINEERING REPORT -DRAFT
December 2024, Page 2
4.2 Alternative 1— Composting........................................................................................................
27
4.2.1
Description..........................................................................................................................27
4.2.2
Design Criteria.....................................................................................................................
31
4.2.3
Map.....................................................................................................................................
32
4.2.4
Environmental Impacts.......................................................................................................34
4.2.5
Land Requirements.............................................................................................................
34
4.2.6
Potential Construction Problems........................................................................................
34
4.2.7
Sustainability Considerations..............................................................................................
34
4.2.8
Cost Estimates.....................................................................................................................
34
4.3 Alternative
2 — Drying and Landfilling........................................................................................
37
4.3.1
Description..........................................................................................................................37
4.3.2
Design Criteria.....................................................................................................................
44
4.3.3
Map.....................................................................................................................................
45
4.3.4
Environmental Impacts.......................................................................................................48
4.3.5
Land Requirements.............................................................................................................48
4.3.6
Potential Construction Problems........................................................................................
48
4.3.7
Sustainability Considerations..............................................................................................
48
4.3.8
Cost Estimates.....................................................................................................................
49
4.4 Alternative
3 — Pyrolysis and Gasification..................................................................................
52
4.4.1
Description..........................................................................................................................52
4.4.2
Design Criteria.....................................................................................................................
55
4.4.3
Map.....................................................................................................................................
56
4.4.4
Environmental Impacts.......................................................................................................59
4.4.5
Land Requirements.............................................................................................................
59
4.4.6
Potential Construction Problems........................................................................................
59
4.4.7
Sustainability Considerations..............................................................................................
59
4.4.8
Cost Estimates.....................................................................................................................
60
4.5 Alternative
4 — Super Critical Water Oxidation..........................................................................
61
4.5.1
Description..........................................................................................................................61
4.5.2
Design Criteria.....................................................................................................................
63
4.5.3
Map.....................................................................................................................................
63
4.5.4
Environmental Impacts.......................................................................................................65
4.5.5
Land Requirements.............................................................................................................
65
4.5.6
Potential Construction Problems........................................................................................
65
4.5.7
Sustainability Considerations..............................................................................................
65
4.5.8
Cost Estimates.....................................................................................................................
66
4.6 Alternative
5 — Dewatering Improvements and Landfilling.......................................................
67
4.6.1
Description..........................................................................................................................67
4.6.2
Design Criteria.....................................................................................................................
70
4.6.3
Map.....................................................................................................................................
70
4.6.4
Environmental Impacts.......................................................................................................72
4.6.5
Land Requirements.............................................................................................................
72
4.6.6
Potential Construction Problems........................................................................................
72
4.6.7
Sustainability Considerations..............................................................................................
72
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PRELIMINARY ENGINEERING REPORT -DRAFT December 2024, Page 3
4.6.8 Cost Estimates.....................................................................................................................
72
4.7 Cost Estimates Summary of Alternatives...................................................................................
74
5.0 Selection of an Alternative.............................................................................................................
74
5.1 Life Cycle Cost Analysis...............................................................................................................
76
5.2 Non -Monetary Factors...............................................................................................................
81
6.0 Proposed Project............................................................................................................................
81
6.1 Preliminary Project Design.........................................................................................................
81
6.2 Project Schedule.........................................................................................................................
85
6.3 Permit Requirements.................................................................................................................
85
6.4 Sustainability Considerations.....................................................................................................
85
6.4.1 Water and Energy Efficiency...............................................................................................
85
6.4.2 Green Infrastructure...........................................................................................................85
6.4.3 Other...................................................................................................................................85
6.5 Project Funding..........................................................................................................................
86
6.5.1 Alternative Selection...........................................................................................................
86
6.5.2 Previous Funding Plan.........................................................................................................
86
6.5.3 Potential Funding Strategies...............................................................................................
86
6.5.4 Recommendations and Next Steps.....................................................................................
87
7.0 Conclusions and Recommendations..............................................................................................
87
List of Tablet
Table 0-1—Alternatives
Costs Summary.................................................................................................... 7
Table 1-1—
Historical Population Data.....................................................................................................
14
Table 1-2 —
City Council Meetings............................................................................................................
16
Table 2-1—
Maximum Allowable Pollutant Concentration......................................................................
18
Table 2-2 —
Kalispell Biosolids Pollutant Concentrations from 2018 to 2023..........................................
19
Table 3-1—
Infrastructure Age and Condition..........................................................................................
22
Table 3-2 —
Industrial Useful Life of Facilities...........................................................................................
25
Table 4-1—
Historical Dry Weight of Biosolids Disposed..........................................................................
26
Table 4-2 —
Design Criteria for Solids Loading to the Alternatives for the Design Year 2044..................
26
Table 4-3 —Advantages
and Disadvantages of Composting.....................................................................
31
Table 4-4—
Design Criteria for Composting Equipment...........................................................................
31
Table 4-5 —
EOPCC for Composting...........................................................................................................
35
Table 4-6 —Annual
OM&R Costs, Disposal Cost, and Life Cycle Costs for Composting ...........................
36
Table 4-7 —
Major Advantages and Disadvantages of Drying...................................................................
44
Table 4-8 —
Design Criteria for Biosolids Drying Equipment.....................................................................
44
Table 4-9 —
Design Criteria for Partial Drying Equipment.........................................................................
44
Table 4-10
— EOPCC for Full Biosolids Drying............................................................................................
49
Table 4-11—Annual
OM&R Costs, Disposal Cost, and Life Cycle Costs for Full Drying ............................
50
Table 4-12
— EOPCC for Partial Biosolids Dryer........................................................................................
50
Table 4-13
—Annual OM&R Costs, Disposal Cost, and Life Cycle Costs for Partial Drying .......................
51
Table 4-14
— Life Cycle Costs Comparison for Komline-Sanderson Partial versus Full Drying .................
51
Table 4-15
— Major Advantages and Disadvantages of Gasification and Pyrolysis ..................................
55
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PRELIMINARY ENGINEERING REPORT -DRAFT
December 2024, Page 4
Table 4-16
— Design Criteria for Pyrolysis and Gasification Equipment ...................................................
55
Table 4-17
— EOPCC for Gasification and Pyrolysis...................................................................................
60
Table 4-18
—Annual OM&R Costs, Disposal Cost, and Life Cycle Costs for Gasification and Pyrolysis....
60
Table 4-19
— Major Advantages and Disadvantages of SWCO.................................................................
63
Table 4-20
— Design Criteria for the AirSCWO System.............................................................................
63
Table 4-21—
EOPCC for SCWO..................................................................................................................
66
Table 4-22
—Annual OM&R Cost, Disposal Cost, and Life Cycle Costs for SCWO....................................
66
Table 4-23
—Advantages and Disadvantages of Dewatering Improvements ...........................................
69
Table 4-24
- Design Criteria for Additional Dewatering Equipment.........................................................
70
Table 4-25
— EOPCC for Dewatering Improvements.................................................................................
72
Table 4-26
— Annual OM&R Costs for the Dewatering Improvements....................................................
73
Table 4-27—Alternatives
Costs Summary................................................................................................
74
Table 5-1—
KT Categories and Criteria......................................................................................................
74
List of Figures
Figure
1-1—
Project Location Map.............................................................................................................. 9
Figure
1-2 —
FEMA Floodplain Map...........................................................................................................
11
Figure1-3
—
Wetland Map........................................................................................................................
12
Figure
1-4 —
Historical Population Data....................................................................................................
14
Figure
1-5 —
Kalispell and Evergreen Population Projections...................................................................
15
Figure
2-1—AWWTP
Existing Facilities.....................................................................................................
17
Figure
3-1—
Projected Biosolids Loading with Population Growth..........................................................
21
Figure
4-1—
Uncovered Aerated Static Pile Composting by ECS..............................................................
29
Figure
4-2 —Bunker
System for Covered Aerated Static Pile Composting by SG ......................................
30
Figure
4-3 —
Map of the Proposed Composting Facility...........................................................................
33
Figure
4-4 —
Example of BCR's Bio-Scru Drying System............................................................................
38
Figure
4-5 —
Example of BioForceTech's BioDryer System.......................................................................
39
Figure
4-6 —
Example of Komline — Sanderson Paddle Dryer...................................................................
40
Figure
4-7 —
Example of ELODE's System and End Product......................................................................
41
Figure
4-8 —
Example of Solar Drying........................................................................................................
42
Figure
4-9 —
Example of Huber Belt Dryer................................................................................................
42
Figure
4-10
— Site Layout of the Installation of the BCR Bio-Scru............................................................
46
Figure
4-11—
Site Layout of the New Solids Handling Building for the BioForceTech BioDryers ............
47
Figure
4-12
— Example of EcoRemedy's Fluid Lift Gasification and Pyrolysis System ..............................
53
Figure
4-13
— Example of BioForceTech's Gasification and Pyrolysis System ..........................................
54
Figure
4-14
— Location of New Solids Handling Building for EcoRemedy Gasification Equipment..........
57
Figure
4-15
— Location of New Solids Handling Building for BioForceTech Pyrolysis Equipment............
58
Figure
4-16
— Schematic of 374Water"s AirSCWO System......................................................................
62
Figure
4-17
— Location of New Solids Handling Building for AirSCWO Equipment ..................................
64
Figure
4-18
—Volute Dewatering Press by PWTech.................................................................................
68
Figure
4-19
— Centrifuge by Andritz..........................................................................................................
69
Figure
4-20
— Map of the Proposed Composting Facility.........................................................................
71
Figure5-1—
KT Analysis Results................................................................................................................
76
Figure
5-2 —All
Alternatives Life Cycle Cost Estimates.............................................................................
78
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PRELIMINARY ENGINEERING REPORT -DRAFT
December 2024, Page 5
Figure 5-3 — Short-listed Alternatives Life Cycle Cost Estimates.............................................................. 79
Figure 5-4 — Highest Scoring Alternatives Life Cycle Cost Estimates........................................................ 80
Figure6-1— Demolition Drawing.............................................................................................................. 82
Figure 6-2 — Preliminary Layout No. 1...................................................................................................... 83
Figure 6-3 — Preliminary Layout No. 2...................................................................................................... 84
List of Appendices
Appendix 1— Uniform Environmental Checklist
Appendix 2 —Agency Comments
Appendix 3 — Environmental Resources Figures
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4+y Res
PRELIMINARY ENGINEERING REPORT -DRAFT
December 2024, Page 6
0.0 EXECUTIVE SUMMARY
0.1 Purpose
The City of Kalispell (City) is pursuing a project to upgrade and expand its current biosolids treatment
and disposal process at their Advanced Wastewater Treatment Plant (AWWTP). This Preliminary
Engineering Report (PER) outlines the current biosolids treatment processes at AWWTP and provides
recommendations for future management alternatives over a 20-year horizon. The condition of existing
facilities are evaluated, various biosolids management alternatives are explored, and a recommended
project is identified considering cost, technical design, environmental impact, and regulatory
compliance.
The AWWTP manages biosolids generated from wastewater treatment. The biosolids are disposed of by
composting at Glacier Gold Composting (GGC) and landfilled at the Flathead County Landfill (Landfill).
GGC has alerted the City that it is closing its Olney, MT composting facility. Furthermore, emerging
contaminant regulations are anticipated that may present challenges for long term land application of
biosolids. Approximately 70% of dewatered biosolids have been composted and sold by GGC. The
remaining 30% are hauled to the landfill. The landfill is considering accepting more biosolids but would
like the dewatered cake to have a higher percent solids content than the average 15% total solids (%TS)
produced by the City now.
The City needs to develop a sustainable, long-term strategy for managing biosolids while meeting
regulatory requirements and minimizing environmental impacts. The projected population growth over
the next 20 years will increase biosolids generation, requiring the adoption of scalable treatment and
disposal methods for increased capacity.
The PER establishes design criteria for biosolids treatment technologies and compares several
alternatives, including composting with land application, drying with landfilling, pyrolysis and gasification
with land application, Super Critical Water Oxidation (SCWO) with land application, and dewatering with
land application.
0.2 Alternatives Considered
In identifying the treatment and disposal goals for the City, one of the following criteria must be met:
A. Maximize biosolids quality to facilitate land application.
B. Maximize dryness to increase landfill acceptance capacity.
Using the criteria listed above five (5) unique alternatives for evaluation were identified as viable long-
term solutions.
1. Composting
2. Drying and Landfilling
3. Pyrolysis and Gasification
4. Supercritical Water Oxidation
5. Dewatering Improvements and Landfilling
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PRELIMINARY ENGINEERING REPORT -DRAFT December 2024, Page 7
Alternative No. 5, Dewatering Improvements with Landfilling is recommended considering both
monetary and non -monetary factors after engineering evaluation, systematic Kepner-TregoeTM (KT)
decision making process, and communications with the City, GGC, and Landfill Staff. The proposed
approach allows the City to proceed with drying (Alternative No. 2) in the future if needed to meet the
landfill operations needs' that may require a wastewater rate increase for Kalispell customers. Bonding
or an SRF loan are planned to complete the proposed project and the amount is within the capital budget
for fiscal year 25. Once a final Alternative is selected, a more robust funding analysis should occur,
including an assessment of community demographics, debt coverage and borrowing capacity, estimated
annual payments under varying funding scenarios, and potential rate impacts.
0.3 Project Costs
The estimated costs for each alternative are summarized in Table 0-1.
2044 Annual OM&R
Costs
2024 Annual Disposal
Costs
Total Annual Costs
(OM&R + Disposal)
20-Year Total OM&R PV
Costs
20-Year Total Disposal
PV Costs
Table 0-1— Alternatives Costs Summary
$217,000
$217,000
$317,000
$42,000
$359,000
$325,000
$13,000
$338,000
$480,000 $104,000'
$6,000 $153,000
$486,000 $257,000'
$4,040,000 $3,900,000 $6,500,000 $9,640,000 $2,120,0001
$- $1,059,000 $330,000 $137,000 $3,920,000
Total Life Cycle Costs $19,937,000 $21,963,000 $62,044,500 $40,342,000 $6,802,000
'OM&R costs for Alternative No. 5, Dewatering with Landfilling are not included in Total Life Cycle Costs as the additional
OM&R to existing operations is anticipated to be insignificant.
1.0 PROJECT PLANNING
1.1 Location
The treatment plant property boundary is located south of the Kalispell City Airport. Airport Way forms
the north and eastern boundary and Airport Rd forms the western boundary. The southwestern extent
of the property borders Ashley Creek. The property consists of 26.22 acres of flat land. The legal
description is as follows: S20, T28 N, R21 W, Acres 26.22, TR 3 IN NW4SW4 & SW4NW4, ASSR#
OOOE000978.
The City owns property to the south of the AWWT near Cemetery Road. The property is approximately
40 acres and is listed as agricultural land based on the Montana Cadastral. The legal description is as
follows: S29, T28 N, R21, Acres 40, TR 5F IN SW4NE4 & SE4NE4.
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PRELIMINARY ENGINEERING REPORT -DRAFT
December 2024, Page 8
Figure 1-1 shows the location of the project in relation to the City and other geological features
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PRELIMINARY ENGINEERING REPORT December 2024, Page 10
1.2 Environmental Resources Present
1.2.1 Soils and Geology
The proposed site is generally flat, with no steep slopes or signs of subsistence. The soils consist primarily
of gravel and alluvium. Any soil instability that may result from construction activities will be managed
through proper excavation and spoils storage.
Agricultural lands in the area surrounding the project do not include any prime or important farm
ground. There are some areas designated as prime farmland if irrigated in the vicinity of the project,
including a portion of the Cemetery Road property. Although a small portion of this prime if irrigated
farmland may be lost if the composting alternative is selected, this minor impact must be weighed
against the agricultural benefit of producing high -quality, locally sourced compost from the City's
biosolids.
1.2.2 Air Quality
The air quality in the area surrounding the proposed site is not in violation of any Clean Air Act standards,
and the proposed project will not have any major impact on air pollution. Minor nuisance odors may
occur if the composing alternative is selected, but these will be mitigated by site location and odor
control design features. The site for the composing alternative is located on Cemetery Road in south
Kalispell, and this City -owned property is not adjacent to any incompatible land uses. The design features
for odor control consist of forced aeration composting methods and possibly covers for the composting
beds. If an advanced treatment alternative is selected, odor control mechanisms will be incorporated
into the emissions control system.
1.2.3 Surface Waters
The primary surface water around the proposed project is Ashely Creek. This creek receives the effluent
discharge from the Kalispell AWWTP in accordance with the City's DEQ permit. The project will not
impact the water quality or quantity in the creek. Any potential sediment runoff from construction
activities will be managed to prevent discharge to the creek, and restoration of disturbed areas will
ensure that the creek is protected after the project is complete. The total area of disturbance will be less
than one acre, so an NPDES permit will not be required.
1.2.4 Floodplains
The project will not impact any flood plains seen in Figure 1-2, all construction actives will be managed
to mitigate floodplain damage or alteration. If avoiding the flood plan is unrealistic, the property
permitting, and agency will be used to mitigate any floodplains damages.
There are no floodplains located on the AWWTP's south property.
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PRELIMINARY ENGINEERING REPORT
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digital flood map. If YI Is not void as Eeserlbed below.
The basemap shown complies with FEMA's basemap
accuracy standards
The flood hazard Infmmatlon Is d.1i"d directly ham the
aulhedtetive NFHL—In servke. prwidetl t, FEM A. This map
a erp.r.d on 10, 29'2024 at 5,46 PM and does not
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time. THe NFHL and effective information may chance ne
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0 250 5Q0 1,Oi]D 1,SOD 2,000- T:b,UUU unmapped and unmademired areas cannot he used for
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Basemap fmagefy So.—: USBS N3fl—1 Map 2023
Figure 1-2 — FEMA Floodplain Map
1.2.5 Wetlands
According to the State of Montana Wetland and Riparian Map, there are no designated wetlands within
the project area. Figure 1-3 shows the extent of designated wetlands in the area.
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e
Figure 1-3 — Wetland Map
There are no wetlands located on or near the AWWTP's south property. If wetlands are located within
the construction area, the appropriate agency will be contacted, and the applicable permits will be
obtained.
1.2.6 Wildlife
The area surrounding the AWWTP is generally urban development. The project would consist of
construction on pre -developed land and will not disturb any wildlife protected areas. See Appendix 2
and Section 1.2.7 for the applicable agency comments regarding endangered species in the area and
appropriate mitigation measures.
1.2.7 Agency Notifications
The following agencies were notified for comments regarding the project.
• Montana Fish Wildlife and Parks — Region 3
• United State Army Corp. of Engineers
• Montana Department of Environmental Quality
• Montana Department of Natural Resources and Conservation
• Montana Historic Preservation Society
• U.S Fish and Wildlife Services
See Appendix 2 for agency correspondence.
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1.2.8 Human Environment
The City of Kalispell has experienced a high rate of population growth in recent years, and the proposed
project will help facilitate this growth trend by providing for current and future wastewater treatment
capacity. Without a practical and reliable means of disposing of its biosolids, the City cannot meet the
needs of current and future residents.
Housing prices have risen considerably because of the City's rapid growth, and meeting the housing
needs of residents inevitably involves increasing the housing supply. The housing supply cannot be
increased without adequate wastewater treatment capacity; thus, the proposed project is essential not
only to sustain growth within the City, but also for increasing the housing stock through new housing
developments in infill projects.
As part of its responsibility to its citizens, the City must also protect public health and safety. A crucial
aspect of this entails providing a means for the treatment and disposal of municipal wastewater
generated within the City. This project is of central importance to the protection of public health and
safety because the treatment, handling, and disposal of biosolids is a key operation performed by the
City's AWWTP.
Another benefit of the proposed prosed project is the indirect impact that it will have on the local tax
base. By providing adequate wastewater treatment capacity, the City can approve new housing
developments and thereby increase its tax base. An expanded tax base will in turn allow the City to
provide better public services for its citizens, maintain and expand its infrastructure, and meet its
financial obligations.
Although the area surrounding the existing AWWTP is already developed, the site on Cemetery Road is
surrounded by agricultural land that could see future development. Areas to the south and east of the
site are zoned for residential and business use respectively. Some impact to future property values in
the area is anticipated if the composting alternative is selected.
Demand for local solid waste disposal facilities will be lessened by the proposed project. The drying and
advanced treatment alternatives discussed below will all result in a reduction in volume of biosolids
requiring disposal. Additionally, the various treatment technologies will generate a high -quality product
that may be put to agricultural use, thereby eliminating the need for landfilling of the biosolids.
1.2.9 Environmental Checklist
The Uniform Environmental Checklist with detailed comments is included in Appendix 1.
1.3 Population Trends
1.3.1 Historic Population Trends
The historical population analysis for this project is based on data from the US Census Bureau as shown
in Table 1-1 and Figure 1-4.
The AWWTP not only services the residents of Kalispell but also the neighboring community of
Evergreen.
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Table 1-1- Historical Population Data
Population
2000 Census 14,160
Population
6,239
Total
PopulationYear
20,399
Period
-
2010 Census
19,927
7,616
27,543
-
20111
19,654
6,790
26,444
-1.0%
20121
20,016
6,696
26,712
1.4%
20131
20,294
6,283
26,577
1.0%
20141
20,629
6,711
27,340
1.3%
20151
21,142
6,955
28,097
1.9%
20161
21,619
7,546
29,165
1.7 %
20171
21,992
7,552
29,544
1.3%
20181
22,621
7,907
30,528
2.1%
20191
23,241
8,002
31,243
2.0%
2020 Census
24,588
1 8,149
32,737
_
4.3%
20212
26,114
7,988
34,102 4.7% l
36,960 6.8%
38,475 3.9%
20222 28,446 8,514
20232 29,886 8,589
Average 2.5%
'American Community Survey (ACS) 5-Year Estimate from US Census Bureau.
2American Community Survey (ACS) 1-Year Estimate from US Census Bureau+
35000
30000
25000
c
0
20000
a 15000
0
10000
5000
0
2500
2000
v
1500
t
1000
c
v
500 v
a
0
�sGs hS4S fsLP SSLP fsLP fsLP SS`P SSLP SS`P SSLP SS`P �sGs SSLP fZ` S�`
Historical Year Kalispell Population tHistorical Change
500
Figure 1-4 - Historical Population Data
The population in Kalispell has been increasing for the past 20 years as shown by the linear trendline in
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Figure 1-4. Like most communities in Montana, Kalispell saw an unprecedented amount of growth
following the 2020 Covid-19 Pandemic. While the growth rate climbed to nearly 7% in 2022, the relative
growth rate has slowed down in recent years.
1.3.2 Population Projections
The average growth for the past 10 years, as seen in Table 1-1, is 2.5%. This growth rate was decided
upon by both AE2S and the City of Kalispell to use for population projections as it reflects a more realistic
growth rate for the next 20-years compared to what was seen recently from the Covid-19 pandemic.
Based upon US Census Bureau most recent ACS data released in May of 2024, the population of Kalispell
and Evergreen is near 40,000 residents.
The projected populations for the residents of Kalispell and Evergreen based on a 2.5% growth rate until
year 2044 are shown in Figure 1-5.
70,000.00
60,000.00
50,000.00
N
i-+
C
Q,1
40,000.00
a�
c
0
30,000.00
a
0
a
20,000.00
10,000.00
Year
■ Kalispell Population ■ Evergreen Population
Figure 1-5 — Kalispell and Evergreen Population Projections
Figure 1-5 shows that the estimated population in 2044 to be 65,300 residents. The City and Evergreen
experience seasonal influxes of tourist and non-resident members, but not to the degree of neighboring
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resort communities in the area. The anticipated non-resident members during the tourist seasons were
deemed inconsequential to populations projects for the City.
It is important to note that the entire population of Evergreen is not served by the AWWTP. The
allowable wastewater flow from Evergreen is 805,000 gpd and the three-year (2021 — 2024) average
flow rate generated by Evergreen is 414,860 gpd for approximately 2,200 accounts. Applying the 2.5%
growth rate to 414,860 gpd for 20-years results in a 20-year design flow rate of 684,000 gpd by 2044.
The design criteria for the project is described in Section 4.1.
1.4 Community Engagement
Discussions describing the project goals and progress have occurred during the City Council meetings
that are open to the public. A summary of the information discussed during the City Board meetings are
shown in
Table 1-2.
Table 1-2 — City Council Meetings
• Identified the contractual agreement with Glacier Gold was done after the 2024
year
March 2024 • Motion approved to continue using Glacier Gold for Composting for 1 more year.
• Identified the need for Engineering Services to analyze biosolid treatment and
disposal alternatives
May 2024 • RFP for Kalispell AWWTP Biosolids Treatment -Disposal Project
August 2024
• Approval of Agreement for Kalispell AWWTP Biosolids Treatment -Disposal Project
with AE2S
December 0 Preliminary Engineering Report —Alternatives Analysis
2024
2.0 EXISTING FACILITIES
2.1 Location Map
Figure 2-1 shows the location of the AWWTP properties in relation to nearby geological features. The
AWWTP property houses the wastewater treatment train and associated buildings, while the south
property is intended for future use.
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PRELIMINARY ENGINEERING REPORT
December 2024, Page 18
2.2 History
The City's AWWTP first began operating in 1992. In 2009 the City completed a plant expansion to
increase from 3.1 million gallons per day (MGD) to 5.4 MGD. Historically the City has had a dual approach
for biosolids disposal. The primary disposal method used is composting. Since 1993 the City has hauled
dewater biosolids to Glacier Gold LLC, where it is mixed with organic material and composted. The
secondary method for disposing of the City's dewatered biosolids is the Flathead County Landfill. The
City began hauling biosolids to the landfill in the early 1990s and has been making weekly deliveries since
2004. By 2018, the City was approaching the delivery capacity limits of Glacier Gold and began exploring
alternative disposal options. In 2019, the Flathead County Landfill agreed to accept up to two loads of
biosolids per week ensuring continued disposal opportunities. The average disposal quantities from 2021
to 2023 are as follows:
• Primary Disposal: Glacier Gold composting facility receives around 533 dry tons/year.
• Secondary Disposal: Flathead County Landfill receives approximately 209 dry tons/year.
2.2.1 Historic Regulations and Compliance
The regulations outlined in 40 Code of Federal Regulations (CFR) 503 govern the management and
application of biosolids. The Environmental Protection Agency (EPA) establishes strict pollutant limits for
various metals, such as arsenic and lead. These rules also establish pathogenic concentration standards
to classify biosolids as Class A or Class B, which affects the disposal method of the Biosolids. Currently,
two compliance methods are defined within 40 CFR 503: the Pollutant Concentration (PC) method and
the Cumulative Pollutant Loading Rate (CPLR) method. The PC method allows for less monitoring if
pollutant levels and below specified thresholds, while the CPLR method requires ongoing monitoring.
The City's biosolids prior to delivery to Glacier Gold and the landfill are classified as Class B. Table 2-1
shows the maximum allowable pollutant concentrations:
Table 2-1— Maximum Allowable Pollutant Concentration
Arsenic (As)
41
Cadmium (Cd)
39
Copper (Cu)
1,500
Lead (Pb)
300
Mercury (Hg)
17
Nickel (Ni)
420
Selenium (Se)
100
Zinc (Zn)
2,800
Source: CFR 503.13 Table 3
Since 2018, the City has not exceeded any of the thresholds for maximum allowable pollutant
concentrations and thus, may use the PC approach to pollutant limit compliance. A summary of the
pollutant concentrations in the City's biosolids over the past six years is provided in Table 2-2.
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Table 2-2 - Kalispell Biosolids Pollutant Concentrations from 2018 to 2023
Moisture
Allowable
Concentration
%
-
98.8
98.2
98.5
99.1
97.8
98.8
98.5
99.5
Ammonia
mg/kg
-
7,345
10,838
13,005
22,410
12,398
9,588
11,880
42,500
Nitrate
mg/kg
-
ND
ND
ND
ND
12.3
ND
4.5
37.0
TKN
mg/kg
-
49,175
90,175
52,025
91,975
117,975
53,100
75,058
292,000
Phosphorus
mg/kg
-
24,850
32,200
30,825
42,700
34,600
26,975
32,315
75,000
Arsenic
Cadmium
mg/kg
mg/kg
41
39
2.00 ND
0.40 0.20
15.0 22.5
205 j__304
17.0 13.0
5.80 7.93
7.33 10.7
2.00 ND
2.25 1.33
Dmgg 0.60
ND 0.93
0.37 1.55
13.3 21.3
219 299
11.5 18.3
5.15 7.08
8.50 13.3
ND 3.78
-
1.75 2.03
575
---------
0.43 ND
ND
ND
17.0
243
10.0
4.05
_ND
1.85
0.50
476
0.73
1.67
ND
ND
157
6.25
3.00
ND
2.08
0.63
9
ND
0.8
0.4
15.4
238.8
12.0
5.6
7.4
1.9
1.3
448
0.4
4.0
3.1
32.0
491.0
30.0
11.0
22.0
8.0 I
_.
5.0
930
1.9
Chromium
Copper
mg/kg
mg/kg
-
1,500
Lead
mg/kg
300
Molybdenum
mg/kg
-
Nickel
mg/kg
420
Selenium
mg/kg
100
Silver
Zinc
M_ercury
mg/kg
mg /
-
,
------
17
Currently, the city delivers fewer than 290 dry metric tons of biosolids to the landfill, in compliance with
its EPA Biosolids Permit MTG-650000, thereby effectively managing its biosolid application while
minimizing environmental impact.
2.3 Condition of Existing Facilities
The City of Kalispell (City) Advanced Wastewater Treatment Plant (AWWTP) biosolids treatment and
disposal infrastructure consists of primary solids wasted from the primary clarifiers that undergo
fermentation, primary and secondary anaerobic digestion, and dewatering by a belt filter press or volute
press. Waste activated sludge (WAS) from the secondary clarifiers is thickened with a Dissolved Air
Flotation Thickener (DAFT) and dewatered with the volute press. The cake achieved is between 13% and
16% total solids (TS).
The conditions and age of the current biosolids treatment and disposal infrastructure as shown in Table
3-1. While most of the equipment is in fair or better condition, most of the infrastructure components
are nearing their design life and replacement or rehabilitation efforts should be planned. The following
improvements are recommended near -term:
Replacement of Belt Filter Press (BFP) polymer feed system.
Replacement of BFP.
DAFT tank demolition and process piping modifications.
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• Replace the nonfunctional WAS pumps to improve the accuracy of WAS flow measurement,
providing better control than the current modulating valve.
These improvements are included in the cost estimate for the proposed project.
2.4 Water/Energy/Waste Audits
The City routinely monitors system performance and repairs pipes, pumps or other elements of their
existing biosolids treatment and disposal infrastructure. This project would more efficiently treat
biosolids, enabling increased handling and disposal. The effectiveness of this project would provide the
City with sustainable options for use and disposal of water, energy, and waste.
3.0 NEED FOR PROJECT
The City is reliant on Glacier Gold composting facility for over 70% of its solids disposal and the landfill
for approximately 30% of its disposal. Although Glacier Gold has been a consistent and reliable partner
to the City, they may close their doors at any time, provided that they give the city one year of warning
before no longer accepting solids for disposal. There is no formal long-term contract with the landfill,
posing further risks to biosolids disposal reliability. The projected population growth of 2.5% per year
over the next 20 years will increase biosolids production, necessitating an evaluation of alternative
treatment and disposal methods to ensure sustainable management.
Kalispell AWWTP needs to expand its capacity limits beyond existing composting and disposal
alternatives and increase the reliability of their solids disposal system. The average dry tons of biosolids
produced during the last three years of available data (2020-2023) projected at 2.5% annual population
growth yields a 2044 projected production of 1260 dry tons per year, as shown in Figure 3-1. Alternative
solutions are needed to ensure regulatory compliance, operational efficiency, and environmental
sustainability.
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140000
120000
100000
80000
60000
40000
20000
0
2024
2029 2034 2039 2044
■ Kal Pop ■ Ever Pop N Total Pop BS Load (dry tons/yr)
Figure 3-1— Projected Biosolids Loading with Population Growth
3.1 Health, Sanitation and Security
The AWWTP is an award -winning wastewater treatment facility and generally meets or exceeds their
discharge and biosolids requirements. The implementation of the project will improve their biosolids
treatment effectiveness to Class A standards and increase disposal capacity.
Planning and executing a long-term sustainable biosolid treatment and disposal project would alleviate
the pressure on the City to manage their biosolids as the population grows. Ultimately a long-term
solution increases the health and safety of the public and the environment. All the proposed alternatives
offer a long-term solution for treatment and disposal, thus providing the city with lasting sustainable
infrastructure for the growing population.
The AWWTP main property is a highly secure plot of land surrounded by a high chain -link fence with gate
accesses. The AWWTP land to the south is relatively undeveloped and if treatment or disposal
infrastructure were to be placed on the land, security measures would have to be implemented for public
safety.
3.2 Aging Infrastructure
Table 3-1 shows the key infrastructure components related to biosolids treatment and disposal and their
relative age and condition at the Kalispell AWWTP.
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Table 3-1— Infrastructure Age and Condition
E
Total capacity of
5,250 GPM, firm
RAS System
capacity (largest
32 with
(valves,
unit out of service)
1992 — With an
15 years
fittings and
of 3,750 GPM,
upgrade in
2017-2022
since
Good
piping)
typical operational
2009
upgrade
capacity of 4,000
GPM
RAS Screw
(1) 15 hp, 1,500
Centrifugal
2009
2024-2029
15
Good
GPM
Pump
RAS
Recessed
(3) Vaughn
Impeller
Chopper Pumps 15
2009
2024-2029
15
Good
Pumps (On
hp, 1,250 GPM
Final
Clarifiers)
(2) Hayward
WAS Screw
Gordan Screw
Poor, Out of
Centrifugal
1992
2007-2012
32
Centrifugal
Service
Pumps
5 hp, 530 GPM
40' Diameter x
2017 — Rehab
TWAS
18.5' depth/
inside conc/w
2059
15
Excellent
Storage
167,000 Gal
coatings
DAFT Float
(standby) 10 hp,
Transfer
10-50 GPM at 3.5%
1992
2007-2012
32
Poor
Pumps,
Solids
Penn Valley
DAFT Float
Transfer
Lead Pump —WAS
Pump
Vogelsang
Fermenter
2009
2024-2029
15
Fair
Elutriation Pump
Rotary
Lobe
DAFT
Horizontal
(2, 1 in operation
Centrifugal
and 1 on standby)
1992
2007-2012
32
Poor
Recycle
15 hp, 150 GPM
Pumps
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DAFT
d11U 1 Un SLdl]UUY)
200 sf, 1.75 Ib/sf/hr 1992
for TWAS with
2.2% solids
2012-2017
Volute 2015 w/ 311
Press 70 GPM WAS 0.7%- Excellent to
(contains 3 1.2% solids screw added in 2030-2035 9 Good
volutes) 2018
Belt Filter
Press (BFP)
2m wide belt,
Solids loading
capacity: 1,290
Ib/hr dry weight 1992
solids
Hydraulic loading
capacity: 86 GPM
at 3.0% solids
2007-2012 32
2009, filter
2019-2024, filter
Faul Air
(2) 51'x42'x7', odor
media
media
Media
15
control
replaced in
replacement
Filter Beds
2015
every 5-7 years
Aluminum
Sulfate
(1) 5,200 gal FRB
(Alum)
*4,800 gal usable
2009
2024-2029
15
Tank
Aluminum
2023 — B&W
(2) metering
Sulfate
dual pump skid
pumps, 25 hp and
2038-2043
1
(Alum)
(not installed
26.9 gph each
Pumps
yet)
DAFT
Polymer
(2) 350 gal each
1992
2030-2035
32
System
FRB
Tanks
DAFT
(2) Metering
Polymer
Pumps, 0.75 hp
1992
2025-2030
32
System
each, 100 gph each
Pumps
BFP
Polymer
(1) 550 gal FRP
1992
2030-2035
32
Tank
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ids Treatment-Disposal/Kalispell W WTP Biosolids Treatment
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Poor
Fair, Dirt
structure is
failing
Good
Good
Fair
Fair
Fair
PRELIMINARY ENGINEERING REPORT
December 2024, Page 24
Polymer
(2) lank mixers
1992
2U25-2u3u 32 Fair
Mixers
BFP
(2) Metering
2025-2030
Polymer
Pumps, 1.5 hp
2008
16 Fair
Pumps
each, 190 gph each
Volute
Press
Polymer
HDPE — Stainless
Activation
Steel skid-
2015
2030-2035 9 Excellent
Chamber:
mounted
Mixing
Tank
Volute
Press
5-100 gph
Polymer
adjustable feed
2015
2025-2030 9 Excellent
Activation
Chamber:
pump
Feed Pump
Volute
Press
High-speed mixer
Polymer
of 1.0 to 1.5%
Activation
polymer by
2015
2030-2035 9 Excellent
Chamber:
volume. Requires
Dilution
water hardness <
Water
400 ppm.
System
Automated
Volute
polymer feed
Press
system monitors
Polymer
and adjusts
Activation
polymer feed pump
2015
2025-2030 9 Excellent
Chamber:
for optimum
SCADA
concentration (22
Controls
active pounds per
dry ton of solids)
Conveys from belt
2010 — New
Dewatered
and filter presses
pans and
Sludge Belt
to disposal/storage
conveyance
2024-2029 15 Good
Conveyor
garage
chain
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Sludge �~ cavity pumps (1- 15
Pumps duty, 1-standby) 15
2009 2024-2029 Good
hp, 200 GPM
The recommended replacement dates of the biosolids treatment and disposal facilities in Table 3-1 were
found using typical industrial useful life estimates and the Facilities Plan Update shown in Table 3-2.
Table 3-2 — Industrial Useful Life of Facilities
Description
Industrial Useful Life
Valves, Fittings and Piping
25-30 years
Pumps
15-20 years
Storage Tanks
40 years
DAFT
20-25 years
Volute Press (contains 3 volutes)
15-20 years
Belt Filter Press (BFP)
15-20 years
Foul Air Media Filter Beds
10-15 years, filter media
replacement every 5-7 years
DAFT Polymer System Tanks
30 years
DAFT Polymer System Pumps
20 years
BFP Polymer Tank
30-40 years
BFP Polymer Mixers
30-40 years
Volute Press Polymer Activation Chamber: Mixing Tank
15-20 years
Volute Press Polymer Activation Chamber: Feed Pump
10-15 years
Volute Press Polymer Activation Chamber: Dilution Water System
15-20 years
Volute Press Polymer Activation Chamber: SCADA Controls
10-15 years
Dewatered Sludge Belt Conveyor
15-20 years
3.3 Reasonable Growth
The City of Kalispell has seen reasonable growth since the start of the of the 2010's. Like most
communities in Montana, the City's population has grown rapidly since the 2020 Covid-19 Pandemic. A
population spike of approximately 7% occurred in 2020 and 2021, which is unprecedented for the City.
Since then, the growth rate has slowed to pre -pandemic numbers and the City is anticipating an average
growth rate of approximately 2.5%. By the design year 2044 the estimated population is approximately
65,300 residents as discussed in Section 1.3.
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4.0 ALTERNATIVES CONSIDERED
The solids treatment and handling alternatives that were analyzed in this PER are as follows:
1. Composting
2. Drying and Landfilling
3. Pyrolysis and Gasification
4. Supercritical Water Oxidation
5. Dewatering Improvements and Landfilling
4.1 Design Criteria
The design criteria used for these analyses is the 20-year projected solids loading at the facility. AE2S
received solids data from the AWWTP starting in 1994. This information is applicable for understanding
historic solids production trends to estimate future solid production over the next twenty years. It is
common engineering practice to statistically summarize the last three (3) years of production and use
that data as a basis for design as shown in Table 4-1.
Table 4-1— Historical Dry Weight of Biosolids Disposed
2021
528
203
731
72:28
2022
541
224
765
71:29
2023
530
199
729
73:27
Maximum
541
224
765
71:29
Average
533
209
742
72:28
To conservatively estimate the 2044 design load, the maximum dry weight in tons was used from the
past three years that was approximately 765 tons in year 2022. A growth rate of 2.5% was used to
estimate the design loading of 1,260 dry tons/year for the year 2044 as shown in Table 4-2.
Table 4-2 — Design Criteria for Solids Loading to the Alternatives for the Design Year 2044
Description
Dewatered Solids Loading (dry tons/year) 1,260
Dewatered Solids TS (%) 15
Dewatered Solids Loading (wet tons/year) 8,400
Regulatory compliance, specifically with 40 CRF 503, is also an important design criterion. As discussed
in section 2.2.1, The City's maximum pollutant concentrations between 2018 and 2023 are less than half
the maximum metal pollutant concentrations outlined in Part 503.13.
If the City's biosolids are within the pathogen standards for Class A biosolids and they meet one of the
vector attraction reductions (VAR) requirements in Part 503.33, they are not required to adhere to the
general requirements or management practices as defined in 503.12 and 503.14. If the City's biosolids
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PRELIMINARY ENGINEERING REPORT December 2024, Page 27
fall within Class B or do not meet one of the VAR requirements, the City must meet both the general
requirements and management practices defined by 503.12 and 503.14. The City's biosolids are Class B.
The management practices in 503.14 state that sewage sludge must be applied to the site at a rate that
is equal to or less than the agronomic rate for the sludge unless otherwise specified by the permitting
authority. The agronomic rate specifically refers to the rate at which nutrients such as nitrogen are
needed by the crop or vegetation on the application site. Sludge must be applied at such a rate as to
minimize the amount of nutrients that may pass through the root zone into the groundwater. The
agronomic rate may therefore become a limiting factor to the sludge application rate depending on the
vegetation present at the site and the nutrient concentrations within the sludge. It is important to
understand the regulatory requirements set forth in 40 CRF 503 as these regulations would be a factor
for disposal methods depending on the alternative selected.
4.2 Alternative 1— Composting
4.2.1 Description
Composting biosolids is a common practice and the process consists of biological degradation of residual
organic matter in an exothermic reaction that reaches pasteurization temperatures between 120°F and
160°F. Properly composted biosolids can be land applied at rates commensurate to the quality and
quality of the biosolids and properties of the land application site considering plants and existing site soil
characteristics. Compost disposal options for the City may include:
• continued partnership with Glacier Gold (unreliable),
• selling or giving away compost to the public,
• partnering with local farmers,
• purchasing land for application that could be leased or farmed, or
• landfilling the final product.
A composting facility can be constructed on the property at the existing AWWTP or at the remote 40-
acre site located at 230 Cemetery Road. The Cemetery Road property was acquired in conjunction with
the EPA and has regulated land use management practices. The disposal site is used occasionallyfor land
applying and tilling digester contents when the digesters are emptied for maintenance. This site could
be used for the composting facility. Increasing the amount of digestion at the AWWTP will reduce the
footprint needed for composting. There are locations at the AWWTP that may accommodate
composting. Advantages of locating composting onsite are utilities (stormwater, wastewater, natural
gas, water, etc.) and odor control at the existing biofilter.
Composting requires adding an amendment or bulking agent to biosolids and aeration or mechanical
turning. Amendments add substrate for decomposition and bulking agents reduce moisture content and
add structure. Commonly used amendments and bulking agents include wood chips, finished compost,
leaves and yard waste, or other green waste that can be sourced from the public. The leaf litter collected
by the City can be used as amendment/bulking agent for composting.
Composting methods include windrow, static pile, and in -vessel. Aerated static pile is evaluated herein
because the quantity of biosolids would require many vessels and windrow does not include forced
aeration and may produce more offensive odors.
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4.2.1.1 Uncovered Aerated Static Pile Composting Overview: Engineered Compost Systems (ECS)
The uncovered composting system consists of a concrete composting pad, aeration system, leachate/
stormwater collection system, dewatered biosolids and amendment mixing system, final product
screening equipment, and storage pad. In this system, the dewatered biosolids are mixed with the
amendment in a pug mill mixer or similar and the mixed product is placed in a static pile on the
composting pad. Air is delivered to the static pile from the bottom through aeration trenches, and the
air can be forced through the static pile (positive), drawn through the pile surface (negative), or a
combination of both strategies (reversing).
Positive aeration is the simplest, most cost-effective aeration strategy but has the highest odors.
Negative aeration has lower odors as a biofilter can be applied to the exhaust gas but the aeration
trenches are more inclined to plugging and this strategy is more expensive than positive aeration due to
more rigorous design considerations. Reversing aeration is the least cost-effective, most complex
strategy but provides the benefits of both positive and negative aeration along with the substantial
process advantage of reducing the temperature gradient throughout the static pile. This results in better
process control and reduces composting time.
A bio-layer of finished unscreened compost or woody amendment is placed on top of the composting
biosolids to act as a cover during primary composting. The nutrient dense liquid that drains from
composting biosolids called leachate is captured in the aeration trenches and is sent back to the
treatment facility or reused for keeping the compost or biofilter moist. Because the bio-layer cover is
permeable, it is required to capture stormwater at the composting facility for treatment.
After an average of 16 days in primary composting, the static pile is moved with a front-end loader to
initiate secondary composting. This physical action of moving compost relieves any compaction and
helps keep the microbes actively composting efficiently. After an average of 24 days in secondary
composting, the compost is screened to remove the woody amendment or other foreign materials, and
the final screened product is stored onsite for final disposal. The final product is Class A with a TS of 25%
to 40% and can be beneficially reused through the public or hauled to the landfill and used as cover. An
example of uncovered aerated static pile composting is shown in Figure 4-1. A large canvas building rated
for local snow and wind loading would be needed to help mitigate odors and visual aesthetics for the
entire uncovered composting facility.
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Figure 4-1— Uncovered Aerated Static Pile Composting by ECS
4.2.1.2 Covered Aerated Static Pile Composting Overview: Sustainable Generations (SG)
A covered composting system includes a concrete composting pad, six concrete bunkers, impermeable
covers with retrieval equipment, aeration system, leachate collection system, dewatered biosolids and
amendment mixing equipment, final product screening equipment, and storage pad. A covered system
operates like an uncovered system as described previously with additional benefits provided by the
covers.
The liquid impermeable cover allows air in and out for healthy composting activity but stops liquid water
from entering or exiting the compost. This barrier completely separates stormwater from leachate and
greatly reduces the amount of water that needs to be treated. The cover has also been shown to reduce
Volatile Organic Compounds (VOCs) and odors in the emissions by >95% and >90% respectively
compared to uncovered composting. This could be a great benefit to the City as utilizing the cover would
mitigate any odor complaints by the public. The cover reduces the drying out of the compost and
promotes more efficient composting similar to in -vessel performance. An example of covered aerated
static pile composting is shown in Figure 4-2. A smaller canvas building rated for local snow and wind
loading would be needed for certain but not all operations to help mitigate odors and visual aesthetics
of the covered composting facility.
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Figure 4-2 —Bunker System for Covered Aerated Static Pile Composting by SG
4.2.1.3 Improvements
The improvements would include the following:
• Construction of a new stretched fabric storage building to contain:
o Mixing equipment
o Final screening equipment
o Dewatered biosolids and amendment storage
o Electrical room
o Front-end loaders
• Construction of a concrete pad for composting and final product storage.
• Installation of all necessary composing equipment.
4.2.1.4 Other Considerations
A major disadvantage of biosolids composting is that there is no destruction of PFAS, and this could
impact the disposal options if an end user is concerned about PFAS. If the end user, whether it is the
landfill or agriculture user, decides to stop accepting composted biosolids from the facility due to PFAS
levels then significant upgrades would need to be completed. If PFAS or other emerging contaminants
became an issue, composting equipment would be abandoned or demolished whereas the drying
equipment discussed in Alternative 2, could potentially be utilized alongside the pyrolysis and
gasification equipment.
The cover that has been used in many successful installations is currently manufactured out of PTFE, a
fluorinated chemical, but starting in 2025, the cover will be manufactured with ePE (expanded
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PRELIMINARY ENGINEERING REPORT December 2024, Page 31
polyethylene). This new chemical is more environmentally friendly than PTFE but has not been
implemented before and therefore has some risk associated with limited installations.
There are additional challenges if the composting facility is located off the AWWTP site. The excess
leachate that is not reused in composting will need to be stored and treated. Table 4-3 highlights the
major advantages and disadvantages of composting.
Table 4-3 — Advantages and Disadvantages of Composting
Advantages Disadvantages
• Operator intensive process.
• Requires obtaining woody
amendment.
• Class A final product. • Requires large area of City's land
• Quality final product with many either at the AWWTP, at the
options for beneficial reuse by Cemetery Road property, or other
the public. offsite location.
Composting • Initial capital investment under • Does not destroy PFAS and this
$16 million. could be an issue for future
• Low OM&R costs. disposal.
• A long history of success even in • Requires management of
similar colder climates. composting product.
• Some additional nutrients are
sent back to the treatment
facility.
4.2.2 Design Criteria
Approximately 1.5 acres is recommended for the entire composting facility with at least 1 acre reserved
for static aerated piles including primary and secondary stages. Table 4-4 shows the design criteria for
composting equipment in addition to those found in Table 4-2.
Table 4-4 — Design Criteria for Composting Equipment
Input Biosolids (dry ton/yr)
Woody Amendment (wet ton/
No. of Aerated Static Piles
Aeration Strategy
Retention Time (days)
Necessary Process Area (acre)
Biofilter Area (ft2)
4.2.3 Map
1,260
7,560
14
Reversing (Primary) and Positive (Secondary)
40 - 80
0.60
893
1,260
6,300
6 Bunkers
Positive
42 - 56
0.50
N/A
The proposed improvements for the installation of a composting facility within the property boundaries
of the AWWTP are shown in Figure 4-3.
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PRELIMINARY ENGINEERING REPORT
December 2024, Page 33
4.2.4 Environmental Impacts
The drying improvements will have minimal detrimental environmental impacts, and overall, a positive
impact on the environment. The potential detrimental impacts would be limited to typical construction
impacts.
A major positive environmental impact is that the final composted biosolids represent a product with
beneficial reuse options. The nutrients retained in the final compost can be reused through land
application and recycled in the environment through bioaccumulation in plants rather than only disposal
at the landfill. This could offset some fertilizer use by the public and therefore offers positive
environmental impacts.
4.2.5 Land Requirements
The City owns the land required for the composting facility.
4.2.6 Potential Construction Problems
No unusual problems are anticipated in the construction of a composting facility. The only issues are the
foreseeable problems associated with construction on an existing facility such as maintaining access to
all facilities and trying to reduce conflicts with operators.
4.2.7 Sustainability Considerations
This alternative is focused on increasing the long-term sustainability of the facility as the biosolids will
be treated to a Class A final product that can be beneficially reused.
4.2.7.1 Water and Energy Efficiency
The project is relatively energy efficient as composting technology is moderately simple and does not
consume significant energy. The aeration blowers consume the most energy, but they are modestly sized
and do not consume substantial energy. The heat necessary for composting and pathogen inactivation
is generated by the metabolism of the biosolids. Water is used to keep the biofilter and biolayer moist
but is consumed in minimal quantities.
4.2.7.2 Green Infrastructure
Green infrastructure considerations are not applicable to this alternative.
4.2.8 Cost Estimates
The Engineer's Opinion for Probable Construction Costs (EOPCC) presented herein are based on 2024
dollars. The opinions are conceptual -level and based upon preliminary equipment cost proposals,
previous project data, engineering judgement, and cost estimating manuals from RS Means, an online
construction cost database. This cost opinion is a Class 4 Estimate based on the definitions of the
Association for Advancement of Cost Engineering (AACE) International.
This level of cost opinion is appropriate for engineering studies and feasibility evaluations to compare
alternatives. The cost opinion at this level of engineering is considered to have an accuracy range of -
30/+50 percent. Actual costs will not be determined until a bidding process has been completed at the
time of construction.
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Contractor overhead and profit is estimated at 15 percent of construction costs. Construction
contingency is assumed to be 15 percent of construction costs and undeveloped design details are
assumed to be 10 percent of construction costs. Construction administration services are estimated at
10 percent of construction cost and engineering, legal, and administration is assumed to be 15 percent
of construction costs. These percentages are used for the EOPCC of each alternative.
A summary of probable construction and capital costs for composting is presented in Table 4-5.
Table 4-5 - EOPCC for Composting
b
Equipment and Quantity Take -off Estimates
Composting Equipment
$1,506,000
$1,593,000
Concrete for Composting Bunkers
$1,750,000
$2,250,000
Leachate/Stormwater Control
$200,000
$100,000
Screening and Mixing Equipment
$500,000
$500,000
Front End Loader
$200,000
$200,000
Amendment Storage and Mixing Building
$150,000
$150,000
Static Pile Metal Building ($30/sq.ft.)
$577,140
N/A
Second Volute Press and Emulsion Polymer System
$922,000
$922,000
Demolition of DAFT Tanks, BFP, and Piping Modifications
$100,000
$100,000
New WAS Pumps
$31,000
$31,000
Cost Allowances and Percentages
Mobilization, Bonds, Insurance (5%)
$485,400
$475,900
Electrical (18%)
$1,069,000
$1,053,000
Instrumentation & Controls (8%)
$475,000
$468,000
Process Piping (10%)
$594,000
$585,000
Site Work (10%)
$594,000
$585,000
Mechanical (HVAC and Plumbing, 10%)
$594,000
$585,000
Architectural (10%)
$59,000
$15,000
Geotechnical (6.5%)
$386,000
$380,000
Subtotal Construction Costs
$10,192,540
$9,992,900
Contractor Overhead and Profit (15%)
$1.529.000
$1.499.000
Undeveloped Design Details (10%)
Construction Contingency (15%)
Construction Cost (w/ Contingency and O&H)
$1,020,000 $1,000,000
$230,000 $225,000
$12,972,000 $12,717,000
Lnglneering, Legal, ana Haminlstratlon (15�pio)
)1,94b,uuU
")1,yUZS,000
Construction Administration (10%)
$1,298,000
$1,272,000
Total Capital Project Costs
$16,216,000
$15,897,000
Low Range (-30%)
$11,351,200
$11,127,900
High Range (+50%)
$24,324,000
$23,845,500
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PRELIMINARY ENGINEERING REPORT December 2024, Page 35
Operation, maintenance, and replacement (OM&R) costs are the recurring costs for electricity and
natural gas, chemicals, operations staffing, maintenance staffing, externalized maintenance issues (e.g.,
paying service professionals to fix pumps), laboratory testing, and the costs to eventually replace parts
and equipment that fail due to wear and tear. The OM&R costs can sometimes justify the selection of a
more expensive capital cost alternative. Regardless of how OM&R estimates are used in alternatives
selection, the estimates can be used for planning for future OM&R budgets.
Power costs were estimated based on a unit cost of $0.11 per kW-hr and natural gas costs were
estimated based on a unit cost of $6.00 per MMBTU and estimated equipment power and natural gas
consumption provided by equipment manufacturers for major equipment. Equipment
maintenance/repair costs are based on equipment lifetime repairs. Annual maintenance costs were
calculated based on the value and complexity of the equipment.
Some treatment methods and equipment packages can require more operator attention and therefore
require a higher estimate for labor cost. Labor requirements were determined by the manufacturer's
and engineer's operational estimates. An average cost of $100,000 per year per employee was used and
includes all wages and benefits. The yearly replacement cost was estimated as 1% of the capital cost of
the equipment.
To estimate the ultimate disposal cost, the yearly quantity of final biosolids is required. The quantity of
final product for disposal each year was estimated by starting from 765 dry tons in 2024 and increasing
the quantity by 2.5% to 1,260 dry tons in 2044. Disposal tipping costs were based on landfilling the final
product at a cost of $35.71 per wet ton (a 15% increase from the current value of $31.05 per wet ton).
Landfill tipping fees are projected to increase at 3% annually after the initial 15% increase. The 3% annual
increase in tipping fees are the same as the projected inflation rate. The discount rate applied to the
projected OM&R costs to convert future dollars to present value is also 3% that equals inflation.
Therefore, disposal cost was held constant at $35.71 for the 20-year projection so that the estimate is in
present value (PV) 2024 dollars. The number of trucks needed to dispose of the annual final product was
estimated using the solids reduction, final TS percentage of each alternative, and a hauling truck volume
of 20 cubic yards. The hauling cost associated with the number of trucks was estimated using a 1-hour
trip to the landfill, an operator wage of $48/hour, and a gas cost of $10 per trip.
OM&R costs were generally prepared based upon buildout flows and loads. The 20-year present value
of the OM&R costs were calculated by multiplying the annual total OM&R cost by 20. The total Life Cycle
Cost was calculated by adding the 20-year PV OM&R cost and the EOPCC as shown in Table 4-6.
These assumptions were applied throughout the OM&R cost estimates for each alternative.
Table 4-6 — Annual OM&R Costs, Disposal Cost, and Life Cycle Costs for Composting
Description• • • •
Power Cost $13,500 $4,000
Operation Labor Cost $148,000 $148,000
Maintenance Cost $20,000 $25,800
Replacement Cost $13,100 $13,900
Amendment Cost $10,000 $10,000
Annual Total $205,000 $202,000
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20-Year Total OMU PV Cost
20-Year Disposal PV Cost
Total Life Cycle Costs
$4,100,000
$0
$20,316,000
$4,040,000
$0
$19,937,000
It was assumed that all compost could be given away or sold to the public with no annual disposal costs.
However, if it was required that the compost be taken to the landfill, the 20-year disposal cost for
composting would add an additional $2.2M.
4.3 Alternative 2 - Drying and Landfilling
4.3.1 Description
Alternative 2 consists of installing biosolids drying equipment for solids handling at the existing facility.
Dewatered biosolids enter the dryer where heat and residence time is used to evaporate most of the
water from the biosolids. This significantly reduces the final volume and increases the quality of the final
biosolids. The biosolids produced by drying are Class A, extremely dry with up to 90% total solids, and
see a total volume reduction of up to 75%.
A substantial quantity of energy is required to heat the biosolids sufficiently for thermal drying. This can
be supplied by burning natural gas, burning biogas from the anaerobic digesters, electricity, or partially
from retaining heat produced bythe metabolic activity of the biosolids. Manytypes of dryers use indirect
heating by utilizing a thermal fluid to heat paddles, a screw, or disks that are in contact with the biosolids,
and this can be energy intensive. Another style utilizes the heat generated by the metabolic activity of
the biosolids. This style also uses direct heating as pre -warmed air is forced through the biosolids, and
this style can be more energy efficient than other styles but is limited to batch processing.
The landfill has requested percent total solids (%TS) for cover material between 40 and 75% to limit dust
production. Manufacturers have verified that dust should not occur for biosolids up to 75% TS, and
operational controls can be installed that make the final product dust free above 75% TS. There are two
sub alternatives: Alternative 2a — Fully Drying and Alternative 2b — Partial Drying, for the purposes of
this report. Alternative 2a - Full Drying considers technologies that produce 90% TS, and Alternative 2b
- Partial Drying consists of technologies that produce between 40 and 75% TS.
4.3.1.1 Alternative 2A —Full Drying
4.3.1.1.1 Indirect Drying System Overview: BCR Bio-Scru
This drying system consists of a dryer, thermal fluid heater, biogas conditioning (if required), exhaust
vapor condenser and odor control, dried biosolids storage, and conveyance equipment. This drying
system can be fed continuously and can accept 13% total solids dewatered biosolids that other dryers
may struggle with and can accept the dewatered solids from the existing volute press. The dewatered
biosolids are fed into the drying chamber that has two screw rotors contacting the biosolids. The hollow
rotors are heated by a thermal fluid that circulates inside them and transfers this heat to the biosolids
for ultimate drying.
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PRELIMINARY ENGINEERING REPORT December 2024, Page 37
The rotors slowly rotate conveying the sludge through the dryer as the water is evaporated and the final
dried product is deposited in an auger that conveys the solids to storage. The steam generated in the
drying process is condensed, set back to the head of the facility, and the residual non -condensable gases
are chemically scrubbed to reduce final odors. The thermal fluid can be heated by a gas -fired (natural
gas or biogas) or electric heater. It should be noted that if biogas is utilized it may need to be conditioned
prior to being combusted in the heater. The final product is Class A/EQ and has characteristics of an
exceptional fertilizer because the nitrogen and phosphorus in the dewatered biosolids remain in the dry
final product. This makes it extremely valuable and opens additional options for disposal.
RIDSULIUS FEED IN
THERMAL FLUID RETURN
THERMAL FLUID SUPPLY
CONDENSATE RETURN
CON'DENSATEsU'PPiY
Figure 4-4 — Example of BCR's Bio-Scru Drying System
4.3.1.1.2 Direct Drying System Overview: BioForceTech BioDryers
This drying system consists of a dewatered biosolids storage system, biosolids dryer, exhaust air wet
scrubber, heating system, air compressor, dried biosolids storage, and necessary conveyance
equipment. This system is not continuously fed and operates in a batch fashion. Each dryer accepts up
to 16,000 Ibs of a minimum of 17% TS biosolids and over the course of 52-72 hours the solids are dried.
Pre -heated warm air is blown through the biosolids to initiate a state of semi -composting and the
biosolids then generate heat that is retained in the BioDryer to help dry the biosolids. Towards the end
of each batch, hotter air is forced into the dryer through the biosolids to dry them to the final TS value.
The exhaust air is cleaned to meet air permits and reduce odors with a wet scrubber. This direct heating
process that recycles the metabolic waste energy present in the biosolids consumes 50% less energy
than typical indirect drying systems. The final product is Class A/EQ and ranges from 70 to 90% TS
depending on the incoming dewatered biosolids. Again, the nitrogen and phosphorus are retained in the
final product and make it extremely valuable opening more avenues for disposal.
Improvements to the existing volute press are required as dewatered biosolids with a solids content
above 17% and optimally >20% TS are necessary for this drying process. This would include installing an
additional press unit or volute to achieve better biosolids dewatering.
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GEAR
GATES 71 RF1T/1D
JU L L trcrLY WHEELS
VALVES
Figure 4-5 — Example of BioForceTech's BioDryer System
4.3.1.2 Alternative 28 — Partial Drying
The following partial drying technologies were identified to meet initial project needs:
- "Scalping" Dryer (Komline Paddle Dryer)
- Electro Osmosis Dehydrator (ELODE)
- Disc Dryer (Huber Disc Dryer RotaDry)
o The smallest unit available is too large for the 20-year solids projections; therefore, this
option has not been evaluated further. This technology is also difficult to operate and
maintain.
Solar Drying (Huber Sludge Turner Solstice)
Belt Dryer (Huber Belt Dryer BT)
Many of these technology manufacturers have requested biosolids testing to confirm performance and
sizing of their equipment.
4.3.1.2.1 Scalping Dryer
Scalping is the process of reducing the biosolids residence time in the drying unit to produce a product
with percent total solids between 45% and 75% rather than 92%. The same unit can still produce 92% TS
but at a significantly reduced throughput such that storage of dewatered feed sludge may be required.
A larger unit is needed for the projected throughput of 1,260 dry tons per year that can produce 92% TS.
The budgetary cost difference between Komline-Sanderson Paddle dryer units that fully dry or scalp an
equal quantity of biosolids is approximately $1M. Some operational risks are associated with scalping
operations as the final product retains significant water and may "gum up" the dryer whereas fully dry
product can move through the dryer easier. The scalping process saves approximately 3,500 MMBTU of
natural gas or $21,000 per year compared to full drying operations. If biogas is used for drying at the
AWWTP then the savings due to scalping goes down. Also, it is estimated that over the course of 20 years
biosolids scalping will cost approximately $1.2M more than full drying for ultimate disposal operations
due to the higher water content in each truckload.
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I
e
Figure 4-6 — Example of Komline — Sanderson Paddle Dryer
A.,
4.3.1.2.2 Electro Osmosis Dehydrator (ELODE)
The ELODE unit can be continuously fed 15% solids that are blended digested primary solids and
undigested waste activated sludge. An electric field is created within the unit between two electrodes
that moves water through the biosolids between the electrodes. Dewatering occurs by the application
of electricity between two electrodes instead of by mechanical force or evaporation by heat. There is
still a mechanical force used in conjunction with the electric current applied similar to a belt filter press
where sludge is evenly distributed on a belt that is pressed between the drum and track to produce 40%
TS.
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15%�5 :. rc Pressed Cake —..... •T r. �;.1. O. ): C rs C.:ke
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Figure 4-7 — Example of ELODE's System and End Product
4.3.1.2.3 Solar Drying
Solar drying consists of a greenhouse building that houses equipment and facilitates air transport over
the biosolids. A large mixer/aerator mixes and blends biosolids to obtain a granular end product. There
is not enough solar energy in Kalispell during winter months and winter storage would be needed. This
technology also requires a large footprint (60,000 sq. ft. or 1.4 acres) in addition to the footprint required
for approximately 4 months of biosolids storage.
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77)
Figure 4-8 — Example of Solar Drying
4.3.1.2.4 Belt Dryer
A belt dryer is fed dewatered sludge by thick sludge progressive cavity pumps that drive extrusion of
biosolids onto the belt. The belt dryer can be fed clean air or air can be recirculated and scrubbed using
a condensation unit. Condensate must be stored and disposed of. There are many fans that circulate air
and the unit for Kalispell has a total estimated load of 110 hp (60 kWh) where the solar drying option
would need approximately half of that power when operating.
Q
Screw press for s!udge dewatering
Condensation unit
(�z
Sludge bunker with thick sludge pumps
Q
Exhaust air scrubber
Pelletizer
Siofilter for exhaust air
Belt Dryer
si
Wastewater heat utilization
Granulate discharge to big baggy.
(Power plant. boiler, heat pump,
open container or silo
r'uO plarr)
Figure 4-9 — Example of Huber
Belt Dryer
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4.3.1.3 Improvements
The improvements for full drying and partial drying using scalping dryer or ELODE dryer would include
the following:
• Add additional volute press for enhanced dewatering of WAS to achieve 18% solids.
• Utilization of the existing Sludge Handling Room in the Process Building to house:
o Drying equipment
• Dewatered biosolids storage (for some technologies)
• Install drying equipment consisting of the dryer, thermal fluid heater, vapor condenser, exhaust
gas scrubbing unit, biogas scrubber (if required), and necessary conveyance equipment.
Installing the BioForceTech dryers a new building would need to be built as well as dewatered biosolids
storage for batching.
Installing solar drying for partial drying would require building an approximately 60,000 ft2 greenhouse
building to house the equipment.
4.3.1.4 Other Considerations
A major disadvantage of biosolids drying is that there is no destruction of PFAS, and this could impact
the disposal options if an end user is concerned about PFAS. If the end user, whether it is the landfill or
agriculture user, decides to stop accepting dried biosolids from the facility due to PFAS levels then
significant upgrades would need to be completed. Gasification and pyrolysis systems would need to be
considered as they can destroy PFAS. BioForceTech supplies a pyrolysis system that works in
coordination with their BioDryers and could be fitted to their system if PFAS destruction ever became a
necessity.
Redundancy is another consideration for drying as installing two dryers for full redundancy is financially
impracticable. As a result, engineering controls will need to be installed to bypass the dryer and convey
dewatered biosolids straight into the hauling trucks in times that the dryer needs to be serviced.
An additional consideration for partial drying is that the final product is no longer Class A/EQ and this
reduces the final disposal options of the dried product.
The BCR dryer can also be used for partial drying and the manufacturer has recommended partially
drying to 80% TS for best operation of the dryer and greatest volume reduction in the final product.
Another reason BCR recommended drying to 80% TS is because drying the biosolids from 80% TS to >90%
TS takes more energy per pound of biosolids than going from 15% TS to 80% TS. This is because drying
to 80% TS evaporates most of the easy to access free water but to go above 80% TS the harder to access
water contained within the bacterial cells of the biosolids takes more energy.
Table 4-7 highlights the major advantages and disadvantages of biosolids drying.
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Table 4-7 — Major Advantages and Disadvantages of Drying
• Class A/EQ final product if fully dried.
• 75% volume reduction in final product
greatly reducing volume for disposal for
fully drying. Partial drying still
substantially reduces the final volume.
• Extremely dry final product with >90% TS
if fully dried.
Biosolids • High quality final product with
Drying concentrated nutrients resulting in more
options for beneficial reuse if fully dried.
• Can use biogas created by Anaerobic
Digesters for indirect heating or heat
generated by metabolic activity in
biosolids therefore reducing operation
costs
• Limited nutrients returned to the head of
the facilitv.
• Relatively high initial capital
costs.
• Operator intensive process.
• High temperature process.
• Can have higher O&M costs.
• May not fit into existing
infrastructure and may
require additional building
for different technologies.
• Does not destroy PFAS and
concentrates PFAS in final
product due to volume
reduction.
• Can have large amounts of
water returned to the head
of the facility if fully dried.
4.3.2 Design Criteria
The drying equipment comes as a package from specific vendors and will be sized according to the design
conditions presented below in Table 4-8 and Table 4-9.
Table 4-8 — Design Criteria for Biosolids Drying Equipment
Dryer Model
----------------
Bio-Scru IC-3600
BioDryer
Batch Size
Continuous
16,000 wet Ibs
Batch Duration
N/A
52 to 72 hours
Minimum Feed Percent Total Solids
13%
17%
Percent Total Solids in Final Product
90%
70% to 90%
Max Solids Loading
1,980 dry tons/year
1,300 dry tons/year
Operating Temperature
Greater than 212°F
Up to 1607
Table 4-9 — Design Criteria for Partial Drying Equipment
Dryer Model 9W-850
Feed Rate (Wet ton/hr) 3,360
Dryer Operation Continuous (100 hrs/week)
Minimum Feed Percent Total Solids 15%
3M
3,360
Continuous
10%
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Percent Total Solids in Final Product
Max Solids Loading
Operating Temperature1.
4.3.3 Map
75%
1,310 dry tons/year
Greater than 2127
40%
1,300 dry tons
Ambient
r
The proposed site layout for the Bio-Scru to be placed in the existing Sludge Handling Room in the
Process Building to scale is shown in Figure 4-10. The partial drying equipment can be installed in the
existing building as well. The BioDryers need additional space and the site layout to scale is found in
Figure 4-11 with an estimate building footprint of 8,100 ft2.
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PRELIMINARY ENGINEERING REPORT
December 2024, Page 47
4.3.4 Environmental Impacts
The drying improvements will have minimal detrimental environmental impacts, and overall, a positive
impact on the environment. The potential detrimental impacts would be limited to typical construction
impacts.
A major positive environmental impact for full drying is reduced biosolids hauling as the volume is
reduced by 75%, greatly reducing the yearly number of trucks required to dispose of the final product.
Even for partial drying the volume is reduced as compared to the current operations. This drastically
reduces greenhouse emissions from hauling.
Another beneficial impact for both partial and full drying is utilizing the biogas created by the anaerobic
digester to heat the dryers. Therefore, the energy contained in the biogas that is constantly generated
at the AWWTP is beneficially utilized to treat the biosolids. This saves the facility significant money but
also saves the facility from needing to burn more natural gas and therefore greatly reduces the
greenhouse gas emissions as compared to drying without utilizing natural gas.
The final product from full drying operations is also of exceptional quality and can be land applied for
beneficial reuse again recycling the nutrient in the environment.
4.3.5 Land Requirements
This project would be constructible entirely within the existing Process Building and does not require
any additional land.
4.3.6 Potential Construction Problems
No unusual problems are anticipated in the construction of a biosolids drying system. The only issues are
the foreseeable problems associated with construction on an existing facility such as maintaining access
to all facilities, trying to reduce conflicts with operators, and maintaining consistent dewatering
operations.
4.3.7 Sustainability Considerations
This alternative is focused on increasing the long-term sustainability of the facility as it greatly reduces
hauling trucks and if the biosolids are fully dried then there are many different disposal options in case
landfilling the final product becomes impracticable in the future.
4.3.7.1 Water and Energy Efficiency
The project is relatively energy efficient as the drying equipment has been designed to retain heat and
to be as energy efficient as possible. However, using electricity or natural gas to heat the dewatered
biosolids consumes a substantial amount of energy. Again, as described above this energy use can be
supplemented with the use of biogas or by using the heat generated by the metabolism of the biosolids
as in the BioDryer. Water is consumed in the wet scrubber of exhaust gas and used in the cooling
conveyers that reduce the temperature of the final product.
4.3.7.2 Green Infrastructure
Green infrastructure considerations are not applicable to this alternative.
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4.3.8 Cost Estimates
A summary of probable construction and capital costs for Alternative 2A, Full Biosolids Drying is
presented in Table 4-10, and the OM&R cost estimates are shown in Table 4-11.
Table 4-10 — EOPCC for Full Biosolids Drying
Description
Equipment and Quantity Take -off Estimates
Drying Equipment
$4,590,000
$8,464,000
Second Volute Press and Emulsion Polymer System
$922,000
$922,000
New Solids Handling Building
NA
$2,835,000
Demolition of DAFT Tanks, BFP, and Piping Modifications
$100,000
NA
New WAS Pumps
$31,000
$31,000
Cost Allowances and Percentages
Mobilization, Bonds, Insurance (5%)
$419,200
$979,300
Electrical (18%)
$1,016,000
$2,206,000
Instrumentation & Controls (8%)
Process Piping (10%)
Site Work (2.5%)
$452,000
$981,000
$565,000
$1,226,000
5142.000
S1.226.000
Mechanical (HVAC and Plumbing, 10%)
Architectural (10%)
Geotechnical (6.5%)
Subtotal Construction Costs
Contractor Overhead and Profit (15%)
$565,000
$1,226,000
NA
$284,000
NA
$185,000
$8,802,200
$20,565,300
$1,321,000
$3,085,000
Undeveloped Design Details (10%)
$881,000
$2,057,000
Construction Contingency (15%)
$1,321,000
$3,085,000
Construction Cost (w/ Contingency and O&H)
$12,326,000
$28,793,000
Engineering, Legal, and Administration (15%)
$1,849,000
$4,319,000
Construction Administration (10%)
$1,233,000
$2,880,000
Total Capital Project Costs
$15,408,000
$35,992,000
Low Range (-30%) $10,785,600
High Range (+50%) $23,112,000
$25,194,400
$53,988,000
Table 4-11— Annual OM&R Costs, Disposal Cost, and Life Cycle Costs for Full Drying
Power Cost
Operation Labor Cost
Maintenance Cost
$33,800
$96,000
$11,700
$26,400
$96,000
$20,000
Replacement Cost
$39,910
$73,600
Natural Gas Cost
$0
$0
Annual Total
$182,000
$216,000
20-Year Total OM&R PV Cost
$3,640,000
$4,320,000
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20-Year Disposal PV Cost $872,000 $980,000
-------------------------------------------------------------------------------------
Total Life Cycle Costs 19,920,000 $41,292,000
It should be noted that these life cycle costs were performed assuming that biogas was utilized in place
of natural gas for heating the dryer. The annual natural gas cost for each dryer is $136,500 for BCR and
$78,000 for BioForceTech and if biogas were not utilized then this would equal an additional $2,720,000
and $1,580,000 respectively added to the life cycle costs of each drying technology.
A summary of probable construction and capital costs for Alternative 213, Partial Biosolids Drying is
presented in Table 4-10, and the OM&R cost estimates are shown in Table 4-11.
Table 4-12 — EOPCC for Partial Biosolids Dryer
Equipment and Quantity Take -off Estimates
Drying Equipment 1 $5,175,000 $1,725,000
Second Volute Press and Emulsion Polymer System $922,000 $922,000
Demolition of DAFT Tanks, BFP, and Piping Modifications $100,000 $100,000
New WAS Pumps $31,000 $31,000
Cost Allowances and Percentages
Mobilization, Bonds, Insurance (5%)
Electrical (18%)
Instrumentation & Controls (8%)
Process Piping / Conveyors (10%)
Site Work (2.5%)
Mechanical (HVAC and Plumbing, 10%)
Architectural (10%)
Geotechnical (6.5%)
Subtotal Construction Costs
Contractor Overhead and Profit (15%)
Undeveloped Design Details (10%)
Construction Contingency (15%)
Construction Cost (w/ Contingency and O&H)
Engineering, Legal, and Administration (15%)
Construction Administration (10%)
Total Capital Project Costs
Low Range (-30%) _
High Range (+50%)
$462,600 $206,400
$1,122,000 $501,000
$499,000 __ __$223,000
$623,000 $278,000
$156,000 $70,000
$623,000 $278,000
NA NA
NA NA
$9,713,600 $4,334,400 J
$1,458,000 $651,000
$972,000 $434,000
$1,458,000 $651,000
$13,602,000 $6,071,000
$2,041,000 $911,000
$1,361,000 $608,000
$17,004,000 $7,590,000
$11,902,800 $5,313,000
$25,506,000 $11,385,000
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Table 4-13 — Annual OM&R Costs, Disposal Cost, and Life Cycle Costs for Partial Drying
Operation Labor Cost
Maintenance Cost
Replacement Cost
Natural Gas Cost
Annual Total
20-Year Total OM&R PV Cost
20-Year Disposal PV Cost
Total Life Cycle Costs
$96,000
$20,000
$45,000
$0
$195,000
$3,900,000
$1,059,000
$21,963,000
$116,000
$20,000
$15, 000
$0
$336,000
$6,720,000
$1,960,000
$16,270,000
These life cycle costs were performed assuming that biogas was utilized in place of natural gas for heating
the dryer. The annual natural gas cost for the Komline-Sanderson dryer is $112,500 and ELODE does not
require natural gas. If biogas were not utilized then this would equal an additional $2,2600,000 to the
life cycle costs of the Komline-Sanderson dryer.
Komline-Sanderson also provided cost estimates for a partial dryer the produces a final product of 45%
TS and a full dryer that produces a final product of 92% TS at build out. The life cycle costs for both
technologies are compared in Table 4-14. Again, these comparisons assume that biogas will be used for
heating both dryers. These values can be compared to the same values for the other full drying
technologies (BCR and BioForceTech) analyzed above.
Table 4-14 — Life Cycle Costs Comparison for Komline-Sanderson Partial versus Full Drying
Partial
EOPCC I $15,433,000 $18,573,000
20-Year Total OM&R PV Cost
20-Year Disposal PV Cost
Total Life Cycle Costs
4.4 Alternative 3 — Pyrolysis and Gasification
4.4.1 Description
$3,800,000
$4,000,000
$1,743,000
$853,000
$20,976,000
$23,426,000
Alternative 3 consists of installing gasification and pyrolysis equipment for solids treatment at the
existing facility. The final solids could then be land applied, hauled to the landfill, used as a beneficial soil
amendment, or used by a topsoil company as a bulking agent. The purpose of this alternative is to greatly
reduce the mass and volume of solids that will need to be disposed of, create a final product of
exceptional quality with many disposal options, and to obtain substantial destruction of PFAS
compounds as well as other contaminants of emerging concern such as microplastics. Biosolids
reductions of up to 90% can be achieved and if the starting biosolids are dewatered to 20% or more the
process can approach energy neutrality.
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Waste activated sludge (WAS) and digested solids are currently dewatered at the facility to 12 — 15%
using a volute press and belt filter press and most gasification and pyrolysis technologies require a
minimum of 18% incoming biosolids. The existing blend of WAS and digested solids has a high heating
value (HHV) of 7,418 Btu/lb which is sufficient to effectively run gasification and pyrolysis as these
processes generally require at least 5,000 Btu/lb. This existing HHV also supports the idea that if biosolids
are dewatered to 20% the process becomes energy neutral.
Additional feedstock of primary/fermented solids could be dewatered and conveyed to the gasification
and pyrolysis equipment. This would completely make digestion redundant and unnecessary, allowing
the City to repurpose the digestors and reduce operating costs.
There are two pyrolysis and gasification manufacturers with installations in the US reviewed in this PER.
This technology is relatively new to the wastewater treatment industry and therefore has sizable
associated risk.
4.4.1.1 EcoRemedy Fluid Lift Gasification and Pyrolysis System Overview
This gasification and pyrolysis system consists of a gasifier/pyrolizer, thermal oxidizer, heat exchanger,
dryer, exhaust gas scrubbing unit, and necessary conveyance equipment. The biosolids dryer operates
at air temperatures up to 1,000 °F and removes excess water from the incoming dewatered sludge to
optimally condition the sludge for gasification and pyrolysis. The gasifier/pyrolizer operates at higher
temperatures of up to 1,800 °F with minimal concentrations of oxygen and in this environment the
biosolids are transformed into energy -rich syngas, Class A/EQ biochar, and ash. The syngas consisting of
H2, CH4, CO, and other byproducts of gasification and pyrolysis is combusted in the thermal oxidizer. A
heat exchanger is used to recover the thermal energy produced in the thermal oxidizer, and the heat is
used to run the biosolids dryer. The exhaust gas from the thermal oxidizer goes through a wet scrubbing
unit to reduce odors and meet air permits.
This system is capable of continuously treating solids as the dried biosolids can constantly be mixed with
the incoming sludge to be the bed material in the gasifier/pyrolizer and this is an attractive feature. The
final product can be split into two different containers for the Class A/EQ biochar and the ash called
FLGSandT`" therefore increasing the overall disposal options. The manufacturer has recommended
running the system to produce almost all FLGSandTm because this results in the greatest reduction is
solids and highest final solids percentage.
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j
Feed Hopper 659r1 ' L
��. Dryer Dryer Solids `
®Feed Air Temp 1,000E Exit 92% f Cake Feed —.
6 % 111 +18%
n
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r�
Figure 4-12 — Example of EcoRemedy's Fluid Lift Gasification and Pyrolysis System
4.4.1.2 BioForceTech Pyrolysis System Overview
This pyrolysis system consists of biosolids dryers, a pyrolysis unit, thermal oxidizer, heat exchanger,
exhaust gas scrubbing unit, and necessary conveyance equipment. The biosolids dryers, called BioDryers,
are unique in that they utilize the heat generated by the metabolic activity of the dewatered biosolids.
A batch of dewatered biosolids enters the dryers and over the course of several days the metabolic
activity heats up the biosolids drying them. The dried biosolids then enter the pyrolysis unit that operates
like the gasifier/pyrolizer previously described. The gas generated is oxidized and the heat is recovered
in a heat exchanger. The recovered heat is used to keep the pyrolysis unit at the necessary temperature,
and some of the heat is recycled to the BioDryers for more effective drying operations. The exhaust gas
goes through a wet scrubber to meet air permits as well.
The final product is mainly Class A/EQ biochar. This system does not operate continuously as the
BioDryers operate in batch fashion to achieve optimal dryness and therefore more engineering
considerations on storage of dewatered biosolids upstream of the dryers is required. BioForceTech has
a low disposal cost guarantee as they have developed markets for beneficial reuse of the final biochar
product called OurCarbon°, and they can facilitate the removal of all biochar from the facility.
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i
CENTRIFUGE
Figure 4-13 — Example of BioForceTech's Gasification and Pyrolysis System
4.4.1.3 Improvements
The improvements would include the following:
• Add additional volute press for enhanced dewatering of WAS to achieve 18% solids.
• Construction of a new solids building to house:
o Gasification and pyrolysis equipment
o Electrical room
o Dewatered biosolids storage (BioForceTech)
• Install gasification and pyrolysis equipment consisting of the gasifier/pyrolizer, thermal oxidizer,
heat exchanger, dryer(s), exhaust gas scrubbing unit, and necessary conveyance equipment.
4.4.1.4 Other Considerations
Fluid Lift Gasification and Pyrolysis can also accept thickened fermented solids that could reduce the
nutrients returned to the head of the plant therefore benefiting overall nutrient removal at the facility.
This would also remove all O&M costs associated with anaerobic digestion such as heating, mixing, and
pumping, and the Anaerobic Digesters could be repurposed to fermenters, additional equalization
tankage, or additional storage volume. Table 4-15 highlights the major advantages and disadvantages of
gasification and pyrolysis.
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Table 4-15 — Major Advantages and Disadvantages of Gasification and Pyrolysis
Gasification
and
Pyrolysis
• Class A/EQ final product.
• More than 92% reduction in Total Solids
for least amount of final product for
disposal.
• Extremely dry final product with >90% TS.
• Effectively destroys 99.9% of PFAS in the
biosolids.
• High quality final product with the most
disposal options for beneficial reuse.
• Uses syngas created with gasification for
biosolids drying and pyrolysis. Reducing
costs associated with natural gas.
• No digestion required.
• Low O&M costs for the quality of the final
product.
• Few nutrients returned to the head of the
facility.
4.4.1.5 Disposal Options
• High initial capital costs.
• Operator intensive
process.
• High temperature
process.
• Very few installations in
the USA creating more
risk.
• More spare parts
required.
• More complex
maintenance if
equipment fails.
• Difficult to fit into existing
infrastructure and require
new building.
The main benefits of gasification and pyrolysis is that the final product has non detect levels of PFAS, is
extremely dry, and is Class A/EQ. This means that the final product has the most disposal options of any
alternative and may reach zero cost for disposal.
1. Landfill
2. Sequestration at City's 40 acres
3. Land application
4. Topsoil amendment
5. BioForceTech facilitation of disposal of OurCarbon°
4.4.2 Design Criteria
The gasification and pyrolysis equipment comes as a package from specific vendors and will be sized
according to the design conditions presented below in Table 4-16.
Table 4-16 — Design Criteria for Pyrolysis and Gasification Equipment
Equipment Name
Max Feed Rate or Max Batch Size
Minimum Feed Biosolids Content
Startup Fuel
Final Product
ECR-432
650 dry Ibs/hr
18%
Biogas or Natural Gas
FLGSand (Ash)
BioDryer and Pyrolysis Unit
16,000 wet Ibs
17%
Natural Gas or Propane
OurCarbon (Biochar)
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Description EcoRemedy BioForceTech
Final Product Class Class A/EQ Class A/EQ
4.4.3 Map
The proposed location of the new building to contain the EcoRemedy gasification equipment to scale is
shown in Figure 4-14. The new building is estimated to have a footprint of 6,000 ft2 based on input from
EcoRemedy. The same building to contain the BioForceTech BioDryers and pyrolysis units is estimated
to have a footprint of 8,100 ft2 based on the sizing of equipment needed at buildout. This is shown in
Figure 4-15.
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4.4.4 Environmental Impacts
The gasification and pyrolysis improvements will have minimal detrimental environmental impacts, and
overall, a positive impact on the environment. The potential detrimental impacts would be limited to
typical construction impacts.
A major positive environmental impact is that the final product does contain very little PFAS and is of
extremely high quality. The final product can be used to enhance soil fertility and has properties that
make it sequester carbon and adsorb additional soil contaminants such as PFAS. Another positive impact
is improved overall nitrogen removal as minimal nutrients in the WAS and digested solids are returned
to the treatment process. Reduced biosolids hauling is another positive as the 90% reduction in volume
greatly reduces the yearly number of trucks required to dispose of the final product thus reducing the
greenhouse emissions from hauling.
Also, the energy contained in the biosolids is completely utilized through gasification and pyrolysis so
that the final product will not decompose and will not create methane or other greenhouse gases at the
landfill making this technology extremely green.
4.4.5 Land Requirements
The City owns the property at the existing WRF, and this project would be constructible entirely within
the property boundary.
4.4.6 Potential Construction Problems
No unusual problems are anticipated in the construction of a gasification and pyrolysis system. The only
issues are the foreseeable problems associated with construction on an existing facility such as
maintaining access to all facilities and trying to reduce conflicts with operators.
4.4.7 Sustainability Considerations
This alternative is focused on increasing the long-term sustainability of the facility as this technology
creates a Class A/EQ final product with many disposal options, requires very few hauling trucks per week
for disposal, and effectively destroys 99.9% of PFAS chemicals. This makes this technology resilient to
future regulations and exceptionally sustainable.
4.4.7.1 Water and Energy Efficiency
The project is energy efficient as the syngas generated in the gasification and pyrolysis step or the
inherent metabolic activity in the biosolids is used to heat the dewatered solids to dry them. This is much
more energy efficient than traditional drying technology that uses natural gas to dry the biosolids. If the
incoming biosolids are dewatered to above 20% then the system starts to get closer to true energy
neutrality and is therefore highly efficient and sustainable. Water is consumed in the wet scrubber of
the exhaust gas but is fed in minimal quantities.
4.4.7.2 Green Infrastructure
Green infrastructure considerations are not applicable to this alternative.
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4.4.8 Cost Estimates
A summary of probable construction and capital costs for gasification and pyrolysis is presented in Table
4-17, and the OM&R cost estimates are shown in Table 4-18.
Table 4-17 — EOPCC for Gasification and Pyrolysis
Description EcoRemedy
Equipment and Quantity Take -off Estimates
Fluid Lift Gasification and Pyrolysis Equipment
$12,880,000
$14,375,000
New Solids Handling Building
$2,100,000
$2,835,000
Dewatered Biosolids Storage and Controls
NA
$750,000
Dewatering Upgrades
$1,000,000
$1,000,000
Cost Allowances and Percentages
Mobilization, Bonds, Insurance (5%)
$1,246,500
$1,502,400
Electrical (18%)
$2,877,000
$3,413,000
Instrumentation & Controls (8%)
$1,279,000
$1,517,000
Process Piping (10%)
$1,598,000
$1,896,000
Site Work (10%)
$1,598,000
$1.598.000
$1,896,000
$1.896.000
Mechanical (HVAC and Plumbine. 10%)
Architectural (10%)
Geotechnical (6.5%)
Subtotal Construction Costs
NA $284,000
NA $185,000
$26,177,000 $31,550,000
Contractor Overhead and Profit (15%)
Undeveloped Design Details (10%)
Construction Contingency (15%)
$3,927,000
$2,617,700
$3,926,550
$4,733,000
$3,155,000
$4,732,500
Construction Cost (w/ Contingency and O&H)
$36,648,250
$44,170,500
Engineering, Legal, and Administration (15%)
$5,498,000
$6,626,000
Construction Administration (10%)
$3,665,000
$4,418,000
Total Capital Project Costs _
Low Range (-30%)
High Range (+50%)
$45,811,250
$32,068,000
$68,717,000
$55,214,500
$38,650,150
$82,821,750
Table 4-18 — Annual OM&R Costs, Disposal Cost, and Life Cycle Costs for Gasification and Pyrolysis
Power Cost
Operation Labor Cost
Maintenance Cost
$58,000
$95,100
$40,000
$50,400
$95,100
$40,000
Replacement Cost
$112,000
$125,000
Natural Gas Cost
$5,000
$14,500
Annual Total
$311,000
$325,000
20-Year Total OM&R PV Cost
$6,220,000
$6,500,000
20-Year Disposal PV Cost
$236,000
$330,000
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Total Life Cycle Costs $52,268,000 $62,045,000
4.5 Alternative 4 — Super Critical Water Oxidation
4.5.1 Description
Alternative 4 consists of installing supercritical water oxidation (SCWO) equipment for solids treatment
at the existing facility. Organic compounds and gases are completely soluble in water under supercritical
conditions (>374°C and 221 bar) whereas inorganic compounds are not, and as a result oxidation
reaction rates are extremely high. Using the unique properties of supercritical water as a solvent and the
oxygen present in air, many compounds in the biosolids are quickly oxidized and the inorganics are
precipitated out of solution. This destruction of many stubborn compounds such as PFAS occurs at
relatively lower temperatures (400°C to 550°C) than other technologies such as gasification due to the
distinctive thermophysical characteristics of super critical water (SCW). The resulting products of SCWO
are clean water, vent gas (primarily CO2 and 1\12), and inorganic salts or oxides.
It should be noted that the final effluent stream from SCWO contains large amounts of water, and the
inorganic material will need to be separated for ultimate disposal. This can be achieved by using a plate
settler to first concentrate the solids and then allowing this concentrate to flow through a bag filter for
final separation and disposal. Solids mass reductions of up to 97% can be achieved, and if all the water
is separated from the final effluent stream this results in a large volume reduction as well. The purpose
of this alternative is to greatly reduce the mass of solids that will need to be disposed of, create a final
product of exceptional quality with many disposal options, and to obtain substantial destruction of PFAS
compounds. Like the other alternatives discussed, the SCWO equipment works more efficiently if the
feedstock is drier, and as the percentage of organic material increases in the feedstock the process can
become better self-sustaining with little energy input.
The specific energy density of the dewatered solids containing a mixture of digested sludge and WAS is
7,400 BTU/Ib and using this value the minimum solids content to successfully operate the AirSCWO is
15% TS with the recommended value being 18% TS. As a result, the existing performance of the volute
press (12% to 15% TS) may not be acceptable, and upgrades may need to be made. It is also
recommended to pretreat the WAS and digested solids prior to entering the AirSCWO system with a 4
mm screen to minimize fouling and reduce the necessary maintenance in the reactor.
4.5.1.1 374Water° System Overview
This SCWO system consists of an AirSCWO reactor, heat exchangers, electric heater, compressor,
separator, cooler, and optional electricity recover unit. To separate the final product from the mineral
effluent a plate settler and bag filter are also required. To protect the reactor 4 mm screens will be
installed as well. The incoming dewatered biosolids are pre-treated in a heat exchanger that uses waste
heat from the final effluent stream to temper the biosolids before entering the reactor. This is done to
help the reactor run more efficiently and operate with less external energy input. The preheated
biosolids then enter the AirSCWO reactor where they are rapidly mixed with the supercritical water and
compressed ambient air, and this rapid mixing brings the biosolids to supercritical conditions. All
oxidation reactions quickly occur in the biosolids (<30 seconds), and the resulting heat is used to
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maintain supercritical conditions as well as preheating the dewatered biosolids prior to entering the
reactor.
The treated stream leaves the reactor still in a supercritical state and needs to be cooled. This cooling
turns the water subcritical, liberates the gases dissolved in the SCW, and the gases are then separated
from the subcritical water. The vent gases can be used to generate electricity making the system more
self-sustaining. The clean gases are vented, and the clean water is ready for disposal. The subcritical
effluent stream then contains all the inorganic salts and oxides that remain. While this system reduces
the mass of solids in the final effluent stream it does not greatly reduce the volume due to much of the
water remaining in the final effluent stream. Therefore, the water must be separated from the remaining
inorganics to reduce the final volume for disposal. This is done by flowing the effluent through a plate
settler to concentrate the minerals and flowing this concentrate through a bag filter to capture the final
product. The ultimate inorganic solids product is a Class A/EQ sand -like material and has a variety of
disposal options. A major benefit of this system is that it can be operated continuously.
COMPRESSOR
AIR mm
Figure 4-16 — Schematic of 374Water°'s AirSCWO System
4.5.1.2 Improvements
The improvements would include the following:
• Add additional volute press for enhanced dewatering.
• Construction of a new solids building to house:
o SCWO equipment
o Electrical room
• Install SCWO equipment consisting of the AirSCWO reactor, heat exchanger, compressor,
separator, expander, and cooler.
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4.5.1.3 Other Consideration.
As previously described, additional solids and water separation technology and prescreening of the solids
would need to be installed after the SCWO equipment for the best results. Table 4-19 highlights the
major advantages and disadvantages of SCWO.
Table 4-19 — Major Advantages and Disadvantages of SWCO
Disadvantages
ClassA/EQfinalproduct. • High initial capital costs.
•
• Up to 97% reduction in Total Solids
for least amount of final product for
disposal if combined with a final
solids/water separation technology.
• Effectively destroys 99.9% of the
PFAS in the biosolids.
SCWO
• High quality final product with the
many disposal options for beneficial
reuse.
• Uses heat from the oxidation
reactions to maintain reactor
temperature therefore reducing
costs associated with natural gas.
• Few nutrients returned to the head
of the facility.
• Operator intensive process.
• High temperature process.
• Extremely new technology to
the municipal wastewater
industry with few installations
and a short operational history.
• More spare parts required.
• More complex maintenance if
equipment fails.
• Requires Prescreening
• Requires small new building to
house the new prescreening
equipment.
• Requires plate settler and bag
filter to capture the final end -
product.
4.5.2 Design Criteria
The SCWO equipment comes as a package from specific vendors and will be sized according to the design
conditions presented below in Table 4-20.
Table 4-20 — Design Criteria for the AirSCWO System
System Model AirSCWO 30
Electricity Generated with Optional Electricity Recovery Unit 2,700 kWh/day
Heat Generated that is Reused in the AirSCWO 12,700 kWh/day
Final Product Produced 0.66 dry ton/day
Clean Effluent Produced 4,800 gallons/day
4.5.3 Map
The proposed new building to contain the SWCO reactor and ancillary equipment to scale are shown in
Figure 4-17. The new building is estimated to have a footprint of 3,700 ft2 based on equipment sizing.
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4.5.4 Environmental Impacts
The SCWO improvements will have minimal detrimental environmental impacts, and overall, a positive
impact on the environment. The potential detrimental impacts would be limited to typical construction
effects.
A major positive environmental impact is that SCWO effectively reduces the quantity of PFAS by >99.9%
in the final effluent stream. SCWO oxidizes the PFAS found in the solids as well as the liquid stream.
Biosolids mass reduction of 97% is another positive because if the final solids are effectively separated
from the water in the final effluent stream, then the yearly number of hauling trucks required to dispose
of the final product is greatly reduced. This reduces the greenhouse emissions from hauling and benefits
the environment.
Like gasification and pyrolysis, the energy contained in the biosolids is completely utilized through SCWO
so that the final product will not decompose and will not create methane or other greenhouse gases at
the landfill making this technology extremely green.
4.5.5 Land Requirements
The City owns the property at the existing WRF, and this project would be constructible entirely within
the property boundary.
4.5.6 Potential Construction Problems
No unusual problems are anticipated in the construction of an AirSCWO system. The only issues are the
foreseeable problems associated with construction on an existing facility such as maintaining access to
all facilities and trying to reduce conflicts with operators.
4.5.7 Sustainability Considerations
This alternative is focused on increasing the long-term sustainability of the facility as this technology
creates a Class A/EQfinal product with many disposal options, requires very few hauling trucks per week
for disposal, and effectively destroys 99.9% of PFAS chemicals. This makes this technology resilient to
future regulations and exceptionally sustainable.
4.5.7.1 Water and Energy Efficiency
The project is energy efficient as the heat from the oxidation reactions is used to maintain supercritical
conditions in the Air SCWO reactor and recycled to preheat the incoming biosolids. The expander also
recovers some energy in the form of electricity that can be used to power the compressor or other
aspects of the SCWO system. These energy recovery controls make the process much more energy
efficient and the technology sustainable. The water present in the biosolids is used for SCWO and very
minimal external water is used in this process.
4.5.7.2 Green Infrastructure
Green infrastructure considerations are not applicable to this alternative.
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4.5.8 Cost Estimates
A summary of probable construction and capital costs for SCWO is presented in Table 4-21, and the
OM&R cost estimates are shown in Table 4-22.
Table 4-21— EOPCC for SCWO
Description 374Watero
Equipment and Quantity Take -off Estimates
SCWO Equipment
$8,632,000
New Solids Handling Building
$428,750
Screening and Settling Equipment
$500,000
Second Volute Press and Emulsion Polymer System
$922,000
Demolition of DAFT Tanks, BFP, and Piping Modifications
$100,000
New WAS Pumps
$31,000
Cost Allowances and Percentages
Mobilization, Bonds, Insurance (5%)
$831,600
Electrical (18%)
$1,911,000
Instrumentation & Controls (8%)
Process Pioine (10%)
$850,000
51.062.000
Site Work (10%)
Mechanical (HVAC and Plumbing, 10%)
Architectural (10%)
Geotechnical (6.5%)
Subtotal Construction Costs
$1,062,000
$1,062,000
$43,000
$28,000
$17,463,350
Contractor Overhead and Profit (15%)
$2,620,000
Undeveloped Design Details (10%)
$1,747,000
Construction Contingency (15%)
$2,620,000
Construction Cost (w/ Contingency and O&H)
$24,451,000
Engineering, Legal, and Administration (15%)
$3,668,000
Construction Administration (10%)
$2,446,000
Total Capital Project Costs
$30,565,000
Low Range (-30%) $21,395,500
High Range (+50%) $45,847,500
Table 4-22 — Annual OM&R Cost, Disposal Cost, and Life Cycle Costs for SCWO
Power Cost $220,000
Operation Labor Cost
$96,000
Maintenance Cost
$67,000
Replacement Cost
$76,000
Natural Gas Cost
$8,700
Mineral Separation Operation Costs
$14,200
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Annual Total $482,000
20-Year Total OM&R PV Cost $9,640,000
20-Year Disposal PV Cost $137,000
Total Life Cycle Costs $40,342,000
4.6 Alternative 5 — Dewatering Improvements and Landfilling
4.6.1 Description
Alternative 5 consists of installing improved dewatering equipment and upgrading the existing biosolids
dewatering operations at the AWWTP to achieve improved dewatering performance and increase the
percent total solids (TS) in the final cake. For this alternative no additional improvements are made post
dewatering that are found in other alternatives as the final dewatered biosolids will be disposed of at
the Flathead County Landfill. The landfill operators request biosolids with a higher solids content (>20%
TS) than the current dewatering process, which typically achieves only 14%-16% TS. Therefore,
improvements to the dewatering operations are necessary to consistently produce biosolids with the
required TS concentration and ensure their continued disposal at the landfill.d.
4.6.1.1 PWTech Volute Dewatering Press
To improve dewatering operations an additional PWTech volute press will be installed in place of the
existing belt filter press that has reached its usable lifespan. This additional volute press unit will be sized
to handle future flows and be able to be operated to produce dewatered biosolids with >20% TS. A
picture of the new volute press is shown in Figure 4-18.
New progressive cavity pumps will be installed upstream of the volute press units to better control the
WAS feed to the units. Currently, WAS is fed to the volute press using a modulating valve on the
pressurized RAS line that attempts to achieve an operator entered flow rate. An issue with the
modulating valve control strategy is that it struggles to maintain constant feed to the volute press.
Additionally, at times the modulating valve has flow breakthrough that washes out the flocculation tank
on the volute press greatly reducing the dewatering performance and this reduces the percent TS in the
final dewatered biosolids.
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Figure 4-18 — Volute Dewatering Press by PWTech
4.6.1.2 Dewatering Centrifuge
Due to the reduced dewaterability of WAS it may be difficult to consistently achieve a dewatered cake
of 20% TS with the volute press. The installation of a centrifuge in place of the existing belt filter press
could address this issue better than another volute press and provide more robust dewatering
operations. A centrifuge can dewater WAS to a higher final percent solids concentration than a volute
press more reliably. However, the higher OM&R costs, increased operational complexity, inability to
continuously produce biosolids for 24 hours, and the high rotational speed associated with a centrifuge
make it less favorable compared to a volute press and may inhibit its installation. A picture of a centrifuge
is shown in Figure 4-19. New WAS pumps will be installed for the best operational control with the
centrifuge as well.
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4.6.1.3 Improvements
The improvements would include the following:
• New PWTech volute dewatering press or centrifuge
• New polymer delivery system
• New progressive cavity pumps
• Additional controls for WAS/Digested Sludge flow metering
December 2024, Page 68
4.6.1.4 Other Considerations
This alternative only improves the current dewatering operations and does not provide additional
biosolids treatment as other alternatives. As a result, there is no destruction of PFAS, and this may impact
future disposal options. However, the dewatering improvements will position the AWWTP to be able to
install biosolids treatment systems such as pyrolysis and gasification easier in the future because these
technologies generally require drier biosolids (20% TS). Table 4-23 highlights the major advantages and
disadvantages of dewatering improvements.
Table 4-23 — Advantages and Disadvantages of Dewatering Improvements
• Lowest life cycle costs. • May struggle at times to meet 20% TS
Dewatering
• Maintains existing if feeding only WAS.
Improvements dewatering and disposal • Landfill may not accept always 20% TS
strategy making it the and then additional improvements will
most operator friendly. need to be made.
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• Maintains free space in
the dewatering building
for future biosolids
improvements.
• Lowest OM&R costs.
• Does not destroy PFAS and this could
be an issue for future disposal.
• 20% TS is still relatively wet and
results in the most hauling trucks,
operator time for disposal, and overall
disposal costs.
4.6.2 Design Criteria
Table 4-24 shows the design criteria for the equipment dewatering improvements in addition to those
found in Table 4-2.
Table 4-24 - Design Criteria for Additional Dewatering Equipment
Model Name
S354
D4
Hydraulic Throughput (gpm)
+--�2-
60 220
Solids Loading (Ibs/hr)
2,600
-----
6,600
------
Installed Power (HP)
1780.5
Max Polymer Consumption (Ibs/dry ton)
22
25
WAS Pump Type
Progressive Cavity
WAS Pump Model
EZ Strip Z38AC_
WAS Pump Capacity (gpm)
160
4.6.3 Map
The proposed improvements for the installation of dewatering improvements within the existing
building are shown in Figure 4-20.
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4.6.4 Environmental Impacts
The dewatering improvements will reduce the number of trucks that the City needs to haul the
dewatered solids to the landfill due to the increased percent solids of the final product. However, the
dewatered solids will be disposed of at the landfill and the beneficial nutrients in the solids will not be
reused as in other alternatives. Also, this alternative has the lowest final percent solids and therefore
requires the most hauling trips resulting in the most greenhouse gas emissions from hauling the final
product to the landfill.
4.6.5 Land Requirements
The dewatering improvements will be placed in an existing building at the AWWTP.
4.6.6 Potential Construction Problems
No unusual problems are anticipated in the addition of dewatering improvements. The only issues are
maintaining the successful dewatering operations while the improvements are installed.
4.6.7 Sustainability Considerations
This alternative increases the long-term sustainability for disposal at the facility as the landfill has the
capacity to receive biosolids for many years to come. However, the long-term sustainability of disposing
of biosolids at the landfill is determined by the landfill operators continually accepting 20% TS dewatered
biosolids. Also, because this alternative does not treat PFAS and other contaminants of emerging
concern (CECs) there is some concern about the long -become disposal at the landfill.
4.6.7.1 Water and Energy Efficiency
The project is energy efficient as the dewatering improvements include energy efficient motors that do
not consume significant energy. Water is only consumed in nominal quantities for wash water in the
volute press or centrifuge.
4.6.7.2 Green Infrastructure
Green infrastructure considerations are not applicable to this alternative.
4.6.8 Cost Estimates
A summary of probable construction and capital costs for the dewatering improvements is presented in
Table 4-25, and the OM&R cost estimates are shown in Table 4-26.
Table 4-25 — EOPCC for Dewatering Improvements
Equipment and Quantity Take -off Estimates
Second Volute Press and Emulsion Polymer System $922,000 $575,000
Demolition of DAFT Tanks, BFP, and Piping Modifications $100,000 $100,000
New WAS Pumps $31,000 $31,000
Cost Allowances and Percentages
Mobilization, Bonds, Insurance (5%) $78,400 $52,600
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Description
Electrical (18%)
$190,000
$128,000
---------------
Instrumentation & Controls (8%)
$85,000
$57,000
Process Piping (10%)
$106,000
$71,000
Site Work (2.5%)
$27,000
$18,000
Mechanical (HVAC and Plumbing, 10%)
$106,000
$71,000
Architectural (10%)
NA
NA
Geotechnical (6.5%)
NA
NA
Subtotal Construction Costs
$1,645,400
$1,103,600
Contractor Overhead and Profit (15%)
$247,000
$166,000
Undeveloped Design Details (10%)
$165,000
$111,000
Construction Contingency (15%)
$247,000
$166,000
Construction Cost (w/ Contingency and O&H)
$2,305,000
$1,547,000
Engineering, Legal, and Administration (15%)
$346,000
$233,000
Construction Administration (10%)
$231,000
$155,000
Total Capital Project Costs
$2,882,000
$1,935,000
Low Range (-30%) $2,017,400 $1,354,500
HiLyh RanLye (+SO%) 54.323.000 52.902.S00
This alternative does not significantly upgrade the existing biosolids handling at the AWWTP as it only
improves existing dewatering operations so it was assumed that the alternative will not incur significant
additional OM&R costs for the existing belt filter press. The OM&R costs of dewatering are not shown in
all previous alternatives to help visualize the additional operations cost differences between each
alternative to existing OM&R costs. Therefore, the 20-year total OM&R costs were not included in the
life cycle cost analysis of this alternative to remain consistent in calculations for comparison purposes.
However, Table 4-26 shows the annual OM&R cost difference between the two dewatering technologies
of the volute press and centrifuge for comparing the two dewatering technologies.
Table 4-26 - Annual OM&R Costs for the Dewatering Improvements
Power Cost
Operation Labor Cost
Polymer Cost
Maintenance Cost
Replacement_ Cos_t_
Annual Total
20-Year Total OM&R PV Cost
20-Year Disposal PV Cost
Total Life Cycle Costs
$10,000
$58,000
$61,000
$61,000
$150,000
$150,000
$26,000
$26,000
$9,000
$5,000
$256,000
$300,000
$0
$0]
$3,920,000
$3,920,000
$6,802,000
i $5,855,000 1
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4.7 Cost Estimates Summary of Alternatives
The estimated costs for each alternative are summarized in Table 4-27.
Table 4-27 — Alternatives Costs Summary
2044 Annual OM&R
Costs $217,000 $317,000 $325,000 $480,000 $104,0001
2024 Annual Disposal
Costs
Total Annual Costs
(OM&R + Disposal)
20-Year Total OM&R PV
Costs
20-Year Total Disposal
PV Costs
$217,000
$42,000
$359,000
$13,000
$338,000
$6,000 $153,000
$486,000 $257,000'
$4,040,000 $3,900,000 $6,500,000 $9,640,000 $2,120,0001
$- $1,059,000 $330,000 $137,000 $3,920,000
Total Life Cycle Costs $19,937,000 $21,963,000 $62,044,500 $40,342,000 $6,802,000
'OM&R costs for Alternative No. 5, Dewatering with Landfilling are not included in Total Life Cycle Costs as the additional
OM&R to existing operations is anticipated to be insignificant.
The equipment vendors provided OM&R estimates for the full buildout design criteria of equipment. The
OM&R costs are not proportional to solids production; therefore, estimating this amount in 2024 dollars
and relating them to solids production annual increase is not accurate. It is conservative to use the full
buildout OM&R costs for conservate budget and planning purposes. The disposal costs are calculated for
annual solids production increases. 2024 disposal costs are used for a total annual cost for budget and
planning purposes.
5.0 SELECTION OF AN ALTERNATIVE
A Kepner-TregoeT`" (KT) decision making process was used to evaluate the alternatives. The process
starts with determining a list of categories and assigning category weights by stakeholders. The selected
categories (and category weight) are economic (30%), technical (33%), social (12%), and environmental
(25%). Criteria and criteria importance factors are developed within each category. A total of 28 criteria
were selected. Criteria importance factors are the average of all the stakeholder assigned values on a
scale of one (least important) to ten (most important). Results are shown in Table 5-1.
Table 5-1— KT Categories and Criteria
Life cycle cost (Capital + 20-Year OW PV)
Initial capital cost
Replacement cost
Operations and maintenance cost
7.3
8.8
7.7
9.0
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Footprint of facility
7.3
Proven effectiveness
9.8
8.3
Flexibility and expandability
Side and waste streams
4.3
No. of additional process units needed
5.3
Ease of operation
7.4
Redundancy of process
6.0
Chemical usage
4.0
Staffing requirements 6.8
CATEGORYO. O.
Public acceptance 6.3
Operator safety 9.9
Public safety 8.3
Climate resilience 5.6
Odor mitigation 7.5
Hazardous material handling 7.5
CATEGORY 4: REGULATORY AND ENVIRONMENTAL CATEGORY (25%) SCORE
Addresses Contaminants of Emerging Concern (PFAS, microplastics, etc.) 7.0
Permitting (air, DEQ approval of novel technologies, etc.)
8.8
Carbon footprint / Energy demand
4.4
Resource (water, energy, etc.) use reduction
5.5
Aesthetics (noise, odor, no. and height of buildings)
4.1
Renewable energy opportunities
2.4
Ease of end -product disposal
7.0
Reliability of disposal 7.7
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Performance scores are assigned using a scale of one (least satisfied) to ten (most satisfied) based on
the ability of each alternative to satisfy the criteria. The performance score is multiplied by the criteria
importance factor and summed for each category. The summed category scores are then normalized by
the maximum summed category score.
The normalized summed category score is then adjusted by the assigned category weight. The weighted
category scores are summed to reach the final liquid train upgrade option score.
Final KT results are shown in Figure 5-1. Dewatering Improvements and Landfilling was the highest
scoring alternative followed closely by Drying and Landfilling based on conversations with the County
Landfill Staff. The landfill is tentatively willing to agree to a short-term (two year) agreement based on
accepting higher %TS solids with dewatering improvements. If landfill operations are negatively
impacted by the higher %TS solids with dewatering improvements only then Alternative 2, Drying and
Landfilling may need to be completed to procure a longer -term agreement with the Landfill.
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Total:
10.0
Total: 9.2
8.5
8.0
6.0
4.0
f
2.0
0.0
Total:
Total:
7.7
7.3
r
2.5
Total:
9.6
Alternative No. 1: Alternative No. 2: Alternative No. 3: Alternative No. 4: Alternative No. 5:
Composting Drying and Pyrolysis and SCWO Dewatering
Landfilling Gasification Improvements
and Landfilling
■ Economic ■ Technical ■ Social ■ Regulatory and Environmental
Figure 5-1— KT Analysis Results
5.1 Life Cycle Cost Analysis
The approach for the Life Cycle Cost Analysis is detailed in Section 4.0. As discussed, the total project life
cycle costs are equal to the sum of the EOPCC and the 20-year PV of OM&R costs. Costs for all alternatives
are compared in Figure 5-2. Error bars represent Low Range (-30%) and High Range (+50%) of capital
costs. Key assumptions include:
- Composting does not require landfill disposal
- Capital cost estimates for all alternatives include dewatering improvements, DAFT tank and BFP
demolition and process piping modifications, and WAS pump replacement
- Dewatering improvements will not add significant OM&R costs to existing operations and these
costs were not included for comparison of all alternatives
- All costs are shown in present value 2024 dollars
Pyrolysis and Gasification and Super Critical Water Oxidation (SCWO) have significantly higher life cycle
costs than the other alternatives. There are anticipated per- and poly-fluoroalkane substances (PFAS)
regulations. PFAS chemicals include more than 12,000 man-made compounds that have been
manufactured since the 1930's. The EPA established drinking water maximum contaminant levels (MCLs)
for six PFAS compounds in April 2024, with compliance required by 2027. Wastewater regulations have
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not been developed yet, but the EPA is expected to release a PFOS & PFOA risk assessment for residuals
and biosolids by the end of 2024.
Preliminary biosolids testing for the AWWTP results are 2 parts per billion (PPB) for PFOS/PFOA and 4.5
PPB cumulative including precursors. These results are low relative to biosolids data available nationally
at this time. Additionally, no significant industrial sources were identified in the City. These results are
promising for continued land application without destructive PFAS technologies Pyrolysis and
Gasification or SCWO based on draft regulations in other States. Considering the monetary and non -
monetary advantages and disadvantages, alternatives were shortlisted to those shown in Figure 5-3.
Composting was the proposed project in the 2018 Kalispell AWWTP Biosolids Management Plan.
However, with uncertainty regarding Glacier Gold Composting, the ease and reliability of disposal with
landfilling, and risk associated with the novel ELODE technology, the highest scoring alternatives were
drying and landfilling and dewatering improvements and landfilling shown in Figure 5-4.
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5.2 Non -Monetary Factors
The Kepner TregoeT`" (KT) Analysis categories, criteria, and performance include many non -monetary
factors as shown in Table 5-1. Other non -monetary considerations including advantages and
disadvantages are detailed for each alternative in Section 4.0.
6.0 PROPOSED PROJECT
The proposed project is Alternative No. 5, Dewatering Improvements and Landfilling based on the
findings documented in this Preliminary Engineering Report.
6.1 Preliminary Project Design
The preliminary design of the project is detailed in Section 4.6 and briefly summarized herein. The project
scope includes the installation of a new dewatering volute press with a dedicated emulsion polymer
dosing system, new WAS pumps, demolition of the existing BFP and dry polymer system, demolition of
the DAFT tanks, and process piping modifications.
The new volute press will match the existing equipment manufacturer, PWTech, but will be a larger
model, ES354. The PWTech equipment provides continual 24-hour operations necessary for the AWWTP
to maintain peak operational performance, versus the centrifuge which can only operate during the day
under plant operator management. The design of the new dewatering volute press will allow for slower
operations than are currently possible and may produce a final dewatered product of 18% to 20% TS.
The new WAS pumps will be the Moyno EZ Strip progressive cavity pump model Z38AC. Figure 6-1
highlights the equipment demolition in the solids handling building.
There are two alternatives for installation of the new dewatering volute press:
1. Installation of the existing and new volute presses near the new WAS pumps where the existing
DAFT system currently is to prepare for the addition of the thermal drying equipment in a future
upgrade. This layout is shown in Figure 6-2 with the thermal drying equipment. This alternative
will incur additional costs for moving the existing volute press to a new location. The space
reserved for the future dryer could be used for storage and maintenance.
2. Installation of the new volute press in place of the belt filter press without DAFT tank demolition
or relocating the existing volute press. If thermal drying is selected in the future, then both volute
presses would need to be moved to accommodate the dryer. This layout is shown in Figure 6-3.
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PRELIMINARY ENGINEERING REPORT
December 2024, Page 84
6.2 Project Schedule
The project schedule will be expedited by the closure of Glacier Gold, although the City did request an
18-month extension of their agreement until September 2026 but have not received approval or
confirmation from GGC.
The proposed project schedule is summarized below:
- January 2025 — March 2025 (3 months): Develop Equipment Procurement Documents
- April 2025 (1 month): Bidding and Equipment Selection
- May 2025 —July 2025 (3 months): Develop Construction Contract Documents
- August 2025 (1 month): Bidding
- September 2025 (1 month): Contractor Selection and Notice to Proceed
- October 2025 — March 2026 (6 months): Construction
6.3 Permit Requirements
The dewatering improvements will be installed in the existing Sludge Handling Room in the Process
Building and will not affect the capacity or discharge of the AWWTP and as a result no new MPDES
permits are anticipated. The City may need to change their EPA biosolids permit show a change in
delivery amounts to a permitted site. However, an updated contract with the Flathead County Landfill
for accepting all the dewatered biosolids from the AWWTP at the improved %TS is highly recommended
to ensure that the biosolids can be reliably disposed of at the completion of this project. The City will
need DEQ approval of plans and specifications and there may be some MPDES permit updates to reflect
that all the biosolids will be landfilled and none will be composted at Glacier Gold. A letter of intent may
be required for the changes in biosolids disposal.
6.4 Sustainability Considerations
This project increases the long-term sustainability for disposal at the facility as long as the landfill has
the capacity to receive biosolids for many years to come. However, the long-term sustainability of
disposing of biosolids at the landfill is determined by the Flathead County Landfill continually accepting
the dewatered biosolids. There is some risk to this as the Landfill management request dewatered
biosolids that are drier and easier to work with than current operations and that the number of weekly
trucks is not excessive.
6.4.1 Water and Energy Efficiency
The project is energy efficient as the dewatering improvements include energy efficient motors that do
not consume significant energy. Water is only consumed in nominal quantities for wash water in the
volute press or centrifuge.
6.4.2 Green Infrastructure
The dewatering improvements will be constructed in the existing Sludge Handling Room in the Process
Building and therefore green infrastructure is not applicable to this project.
6.4.3 Other
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This project has the most operational simplicity of all the alternatives analyzed. The major dewatering
improvement of installing a new volute press retains the operator knowledge as the equipment matches
existing equipment and therefore there will not be a steep learning curve for operators at the AWWTP
that would have occurred for other alternatives.
6.5 Project Funding
6.5.1 Alternative Selection
The City is weighing several funding options for the Biosolids Treatment and Disposal Project, which
relies on the selection of a final Alternative. The proposed options vary in scope and scale, with the least
expensive estimated at several million dollars and the more costly options exceeding $20.0 million. Given
this wide range, establishing a funding strategy at this stage is challenging and uncertain, and the City
plans to update this section once their City Concil provides direction regarding their preferred
Alternative.
Beyond upfront capital costs, the City has also considered impacts to their annual operating budget, such
as increases necessary for powering and operating new equipment and added tipping fees. Like capital
costs, wide variations in operating costs also exist based on Alternative. Upon initial review, the City
determined that the overall financial impacts of operating the new equipment will be negligible (under
most Alternatives) since the options will repursue existing budget line items that are similar in overall
amounts rather than requiring line -item additions and increased totals.
For example, the City spends approximately $160,000 a year hauling their biosolids to Glacier Gold under
current conditions. Under Alternative No. 5, these hauling costs would be similar even though disposal
would shift to the landfill. Given this, it is assumed that any changes to operating costs would be a minor
fraction of the City's existing operating budget and not warrant any rate increases to fund. This
assumption may need to be reevaluated once the City formally selects an Alternative.
6.5.2 Previous Funding Plan
The City has been proactive in its financial planning for the Biosolids Treatment and Disposal Project. A
$9.5 million expense was included in their most recent budget, including a plan to use a combination of
rate revenue, cash reserves, and revenue bonds to fund the total.
The City has a variety of sewer and stormwater loans backed by rate revenue in place or near finalization,
with an annual payment amount of approximately $2.0 million per year. A notable reduction will occur
in 2028, reducing their existing debt obligations by nearly 50% to approximately $1.0 million per year.
6.5.3 Potential Funding Strategies
Given that bonding is the City's prioritized funding strategy, this section provides several advantages and
disadvantages of the two primary options available in Montana, including traditional market financing
and the Montana Water Pollution Control State Revolving Fund (SRF). Each source must be weighed
carefully, and ultimate decisions on which option to pursue should be made based on overall City goals,
including timing, administrative overhead, federal crosscutters, grant ratio desire, and interest rates.
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Traditional market financing typically yields higher interest rates compared to State and Federal sources;
however, they can provide the greatest flexibility and typically the least amount of time to acquire.
Interest rates can vary, and consultation with the City's Municipal Financial Advisor is necessary to learn
the latest terms and borrowing requirements. The main benefit of traditional financing is that funding is
relatively easy to acquire and does not warrant compliance with State and Federal requirements, such
as Build America Buy America (BABA), National Environmental Protection Act (NEPA), and Davis -Bacon
Wages. The drawback is that interest rates track with the market, with no grant and loan forgiveness
benefits available. Traditional bonding is advantageous for agencies seeking rapid funding, or in cases
where agency funding sources lack partial or full capacity.
The second bonding source is SRF, which offers low -interest loans for up to 30 years. Current rates are
2.5% on the State's website; however, they are subject to change based on timing and ultimate
borrowing terms. The City is well -versed in acquiring SRF loans and the process that entails. It is
important to note that acquiring SRF funding can take over a year to complete and invoke several State
and Federal regulations that may impact construction timelines and elevate estimated costs. Initial
consultation was held with SRF staff, and they gave a preliminary indication that the City could request
up to $20.0 million, and that there would be up to $1.0 million in grants available through their Emerging
Contaminant Fund and up to $1.0 million available in Loan Forgiveness. The remainder of the costs would
be financed by a traditional low -interest SRF loan package for a 20-to-30-year payback period.
Other funding options beyond bonding the City may pursue include several State and Federal grants,
such as those available from the Department of Natural Resource Renewable Resource Program, the
Department of Commerce Coal Endowment Program, and Congressionally Directed Spending (i.e.,
earmarks). Another is to acquire a loan through EPA's Water Infrastructure Finance Act (WIFIA), which
could fund up to 49% of eligible project costs and would allow the City to defer payments for up to five
years. This would take advantage of the City's drop in debt obligations in 2028, especially if one of the
more expensive Alternatives is pursued. Decisions regarding the pursuit of these other funding sources
outside of bonding will be made once the scope and scale of the Biosolids Treatment and Disposal Project
is determined.
6.5.4 Recommendations and Next Steps
The primary recommendation at this stage is to continue to engage key funding agencies, like SRF, to
understand opportunities around application timing and potential grant opportunities. This work should
be completed in tandem with City Council -level conversations regarding the selection of an Alternative
and overall project timing. Once a final Alternative is selected, a more robust funding analysis should
occur, including an assessment of community demographics, debt coverage and borrowing capacity,
estimated annual payments under varying funding scenarios, and potential rate impacts.
7.000NCLUSIONS AND RECOMMENDATIONS
It is recommended that the City proceed with Alternative No. 5, the dewatering improvements and a
pursue a landfill agreement.
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PRELIMINARY ENGINEERING REPORT
December 2024, Page 87
The City does not have sufficient cash to fund the dewatering project without bonding or an SRF loan,
and a financial review will be required to assess rate impacts. The proposed alternative allows the City
to transition to a drying process (Alternative No. 2) in the future, if necessary, to meet landfill operation
requirements; however, this may lead to a wastewater rate increase for Kalispell customers
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CITY OF
KALISPELL
SIDEWALK AND TRAILS ASSESSMENT DISTRICT SUB -COMMITTEE
DRAFT MEETING MINUTES
October 21, 2024, Immediately Following Regular Meeting
First Floor Conference Room, City Hall, 201 First Avenue East
Audio of this meeting with time stamped minutes can be found at:
https://www.kalispell.com/480/Meetin2-Videos.
Links are to audio; video is not available.
A. CALL TO ORDER
The meeting was called to order at about 7:10 pm.
Council Members Jed Fisher, Ryan Hunter and Chad Graham make up the Sub -Committee and
were in attendance.
Staff present included City Manager Doug Russell and City Clerk Aimee Brunckhorst.
B. DISCUSSION
Initial Subcommittee Discussion for Sidewalk, Trails, Etc., Assessment District
City Manager Doug Russell began the meeting explaining that the Sub -Committee goals are
identifying what categories the committee would like to look at, and then staff can bring back
more information for committee discussion related to prioritizing projects and look at a 10-year
timeframe. The committee would then report back to the full Council for any decisions.
The categories that Mr. Russell brought forward as a starting point for discussion included:
Sidewalk Replacement
Sidewalk Installation — expansion of 50/50 program
ADA — Intersections — expansion
Trails Maintenance
Traffic Control — Need more information
New Trails
Mr. Russell asked whether these categories are appropriate and if the committee would like to
add additional categories.
Kalispell Sidewalk Trails Sub -Committee Minutes, October 21, 2024
00:02:54 Council Member Hunter asked for clarification related to trails. He then spoke to his
desire to add a category for protected bike lanes or shared use roads. He spoke about prioritizing
projects that would not have other avenues for funding.
00:04:38 Council Member Hunter spoke regarding prioritizing each year understanding that not
all categories could be funded each year.
00:05:43 Council Member Hunter spoke regarding his vision for the traffic controls category as
items like traffic circles, bump -out curbs, and possibly traffic islands if they would not be funded
through a road project and referred to the Safety Action Plan.
00:06:53 Council Member Fisher agreed that the categories seem appropriate.
00:07:05 Council Member Graham asked about resistance from homeowners related to sidewalk
installation and subsequent maintenance responsibilities of the homeowner.
00:08:15 Council Member Hunter spoke regarding supplementing the 50/50 sidewalk program
with full replacement. He would like to see the City fully fund replacement of sidewalks.
City Manager Russell spoke regarding policy decisions being the purview of the full Council. He
spoke regarding bringing forward costs for consideration.
00:10:15 Council Member Fisher spoke regarding his past experience related to building trails
for the County and asked about and spoke regarding the importance of trail maintenance upkeep
on current trails.
00:11:07 Council Member Fisher asked about other trail funding mechanisms.
City Manager Russell spoke regarding projects that have been funded and then answered
questions about grant fund matching sources.
00:12:50 Council Member Graham spoke to the need for maintenance to be included in bike
lanes and his concerns related to managing reasonable maintenance expectations especially in the
winter.
00:14:11 City Manager Russell spoke to policy questions being discussed by the full Council and
the importance of including maintenance into an assessment district.
00:16:10 Council Member Fisher spoke regarding maintenance and liability concerns.
00:16:46 City Manager Russell asked for initial thoughts related to a 10-year horizon for each
category and then discussions regarding prioritizing.
Page 2 of 4
Kalispell Sidewalk Trails Sub -Committee Minutes, October 21, 2024
00:17:40 Council Member Hunter spoke regarding the need for flexibility and keeping the
options broad. He then spoke regarding prioritizing so that the District costs would be
reasonable.
00:19:49 Council Member Fisher asked whether costs were included in the completed Main
Street Safety Action Plan. Staff spoke regarding gathering general costs.
00:21:20 Council Member Fisher asked how the District would be brought before voters, and
Council and staff talked about offering Council options to discuss.
00:22:34 Council Member Graham spoke regarding the possibility of an option that would
address current problems with things like sidewalks and trails maintenance and replacement, and
looking at wants versus needs.
00:25:12 Council Member Fisher spoke regarding the existing maintenance and responsibilities
and having a way to fund safe current trails before moving forward. He spoke further regarding
trail lifespans and full rebuilds.
00:26:59 City Manager Russell spoke regarding going to staff for further information to come
back to the Sub -Committee with.
C. PUBLIC COMMENT
00:27:30 Scott Daumiller, Public Comment
Daumiller spoke to his concerns related to the cost of property taxes. He spoke regarding a
neighbor's struggle paying for replacement of her damaged sidewalks. He would like to see a cap
on property taxes and spoke regarding many people struggling to stay in their homes when
property taxes increase. He provided examples of road engineering decisions made by the City
and by Montana Department of Transportation that he does not agree with and ways in which he
believes they are not appropriate. He spoke to frustration that taxpayers pay for traffic
engineering he does not agree with. He spoke regarding history of funding for trail maintenance
prior to the 1980's. He asked that the old infrastructure be taken care of as well as the people
paying for it.
00:36:56 RoseAskviz Public Comment
Ms. Askvig spoke regarding the difficulties in keeping everyone happy. She spoke to her belief
that taking care of current infrastructure is important prior to moving forward. She appreciates
the idea of multiple options and prioritizing and feels excited.
Seeing no further public comment, public comment was closed.
Daumiller spoke further regarding his views and regarding trail safety issues.
Page 3 of 4
Kalispell Sidewalk Trails Sub -Committee Minutes, October 21, 2024
Public comment received to Mayor and Council via email to publiccommentgkali spell. com can
be seen at
https://time. ci. kalispell. mt.us/WebLink/Browse. aspx?id=128274&dbid=0&repo=Kalispell.
Manager Russell said that staff will gather information to bring back to the Sub -Committee and
will schedule the next meeting after that can be compiled.
D. ADJOURNMENT
Staff adjourned the meeting at about 7:52 p.m.
Aimee Brunckhorst, CMC
City Clerk
Minutes approved on 2024
Page 4 of 4
CITY OF
KALISPELL
City of Kalispell
201 1st Ave E. P.O. Box 1997
Kalispell, Montana 59903-1997
(406) 758-7000 Fax (406)7757
REPORT TO: Sidewalk and Trails Assessment District Subcommittee
FROM: Doug Russell, City Manager
SUBJECT: Review of funding allocation model
MEETING DATE: December 9. 2024 (following Council work session)
BACKGROUND: In furthering discussion on a potential assessment district related to
sidewalk construction and maintenance, trail construction and maintenance, traffic control
improvements, and bike lane development and maintenance, we have collected information
related to costs for the various categories of improvements. Using these cost estimates, we have
assembled a funding allocation model. This model contains numerous variables that can be
adjusted as it relates to assessment levels, work categories, and outcome levels. Prior to further
discussion on the respective variables, it is important to introduce the subcommittee to this
model, and how adjustments to the variables impact the overall outcomes. As such, the
subcommittee meeting on December 9 is anticipated to simply be an overview of the allocation
model. Future meetings will entail discussions related to the respective categories of work,
assessment levels, allocations, and service delivery outcomes.
RECOMMENDATION: It is recommended that the subcommittee review and discuss the
funding allocation model in preparation for future meetings where the merits of the respective
variables will be discussed.