Wastewater Treatment Facility Master Plan by JVA Oct 2024.pdf

WASTEWATER TREATMENT FACILITY MASTER PLAN

FOR THE

TOWN OF LYONS

SEPTEMBER 2024

WASTEWATER TREATMENT FACILITY MASTER PLAN

FOR THE

TOWN OF LYONS

JVA, Inc.

1319 Spruce Street

Boulder, CO 80302 phone: 303-444-1951 fax: 303-444-1957

JVA Project No. 240558.ENV

SEPTEMBER 2024

Town of Lyons Wastewater Treatment Facility Master Plan i

TABLE OF CONTENTS

EXECUTIVE SUMMARY

BACKGROUND AND PURPOSE

SCOPE

PLANNING PERIOD

SUMMARY OF TREATMENT ALTERNATIVES

RECOMMENDED ALTERNATIVE

FUNDING OPPORTUNITIES

SECTION 1 – EXISTING CONDITIONS

PLANNING AND SERVICE AREA

HISTORICAL POPULATION

CURRENT WASTEWATER FLOWS AND LOADS

EXISTING FLOWS

EXISTING LOADING

PERMIT COMPLIANCE

SECTION 2 – CONDITION AND PERFORMANCE ASSESSMENT

EXISTING WASTEWATER TREATMENT FACILITY LAYOUT AND DESCRIPTION

PRELIMINARY PROCESSES

INFLUENT FLOW MONITORING

INFLUENT SAMPLING

HEADWORKS ROOM

MECHANICAL SCREENING AND BYPASS SCREEN

GRIT REMOVAL

SCUM REMOVAL AND SPLITTER BOX

SECONDARY TREATMENT

SBR AERATION AND MIXING

EFFLUENT EQUALIZATION

ALKALINITY ADJUSTMENT

DISINFECTION AND NON-POTABLE WATER SYSTEM

SOLIDS HANDLING

ODOR CONTROL

POWER AND CONTROLS

PERFORMANCE ASSESSMENT AND LIMITING FACTORS

PRELIMINARY PROCESSES

CONDITION AND PERFORMANCE ASSESSMENT

PERFORMANCE LIMITING FACTORS

SECONDARY TREATMENT

CONDITION AND PERFORMANCE ASSESSMENT

PERFORMANCE LIMITING FACTORS

DISINFECTION

CONDITION AND PERFORMANCE ASSESSMENT

Wastewater Treatment Facility Master Plan ii

PERFORMANCE LIMITING FACTORS

SOLIDS HANDLING

CONDITION AND PERFORMANCE ASSESSMENT

PERFORMANCE LIMITING FACTORS

ODOR CONTROL

CONDITION AND PERFORMANCE ASSESSMENT

PERFORMANCE LIMITING FACTORS

POWER AND CONTROLS

CONDITION AND PERFORMANCE ASSESSMENT

PERFORMANCE LIMITING FACTORS

FLOODPLAIN ISSUES

SECTION 3 – FUTURE CONDITIONS

POPULATION AND LAND USE PROJECTIONS

WASTEWATER FLOW AND LOADING FORECASTS

PEAKING FACTOR

FLOW PROJECTIONS

LOADING PROJECTIONS

ALTERNATIVE ORGANIC CAPACITY

FUTURE REGULATIONS

SECTION 4 – WASTEWATER TREATMENT ALTERNATIVES ANALYSIS

CONSOLIDATION WITH LONGMONT

SECONDARY TREATMENT ALTERNATIVES

SEQUENCING BATCH REACTOR (SBR) EXPANSION

ADVANTAGES

DISADVANTAGES

AEROBIC GRANULAR SLUDGE (AGS)

ADVANTAGES

DISADVANTAGES

MEMBRANE BIOREACTOR (MBR)

ADVANTAGES

DISADVANTAGES

DIGESTION IMPROVEMENTS

DEWATERING ALTERNATIVES

SCREW PRESS

ROTARY FAN PRESS

WWTF IMPROVEMENTS

PRELIMINARY PROCESSES

IPS UPGRADES

WET WELL UPSIZE

SPLITTER BOX REHAB

REDIRECT SIDE STREAM FLOWS

SECONDARY TREATMENT

AERATION CAPACITY UPGRADES

Wastewater Treatment Facility Master Plan iii

DISINFECTION

POST EQ BASIN PUMPS UPGRADES

REPLACE AND UPGRADE UV SYSTEM

NPW SYSTEM RELOCATE

SOLIDS HANDLING

REPLACE CENTRIFUGE

ASHT UPGRADES

ODOR CONTROL

POWER AND CONTROL

SECTION 5 – RECOMMENDED ALTERNATIVE

OPINION OF PROBABLE COST

EVALUATION OF ALTERNATIVES

MENU OF OPTIONS

RECOMMENDATIONS

PRELIMINARY PROCESSES

SECONDARY TREATMENT

DISINFECTION

DIGESTION

DEWATERING

MISCELLANEOUS

IMPLEMENTATION SCHEDULE

SECTION 6 – FUNDING OPPORTUNITIES

BIPARTISAN INFRASTRUCTURE LAW

STATE REVOLVING FUND – LOW INTEREST LOANS

USDA, RURAL DEVELOPMENT

DEPARTMENT OF LOCAL AFFAIRS ENERGY AND MINERAL IMPACT ASSISTANCE FUND

ADMINISTRATIVE GRANTS

TIER I GRANTS

TIER II GRANTS

COMMUNITY DEVELOPMENT BLOCK GRANTS (CDBG)

SMALL SYSTEMS TRAINING AND TECHNICAL ASSISTANCE (SSTA) GRANTS

WATER QUALITY IMPROVEMENT FUND (WQIF) GRANTS

COLORADO WATER RESOURCES AND POWER DEVELOPMENT AUTHORITY GRANT ASSISTANCE

PROGRAM (GAP) FOR SMALL SYSTEMS

COLORADO WATER CONSERVATION BOARD (CWCB)

FLOOD AND DROUGHT RESPONSE FUND

WATER PROJECT LOAN PROGRAM

Wastewater Treatment Facility Master Plan iv

LIST OF TABLES

TABLE 1 – LOADING SCENARIO SUMMARY

TABLE 2 – DECISION MATRIX FOR SECONDARY TREATMENT ALTERNATIVES

TABLE 3 – WWTF IMPROVEMENT OPTIONS

TABLE 4 – HISTORICAL POPULATION FROM 2000 TO 2022

TABLE 5 – WWTF INFLUENT FLOW FROM JUNE 2021 THOUGHT MAY 2024

TABLE 6 – INFLUENT LOADING SUMMARY FROM JUNE 2021 TO MAY 2024

TABLE 7 – SUMMARY OF PERMIT VIOLATIONS

TABLE 8 – POPULATION PROJECTION

TABLE 9 – PEAK HOUR FACTOR

TABLE 10 – PROJECTED AVERAGE AND PEAK HOUR INFLUENT WASTEWATER FLOW

TABLE 11 – LOADING PROJECTIONS

TABLE 12 – DESIGN BASIS APPROACHES

TABLE 13 – COST SUMMARY OF CONSOLIDATION

TABLE 14 – DECISION MATRIX FOR SECONDARY TREATMENT ALTERNATIVES

TABLE 15 – WWTF IMPROVEMENT OPTIONS

LIST OF FIGURES

FIGURE 1 – LYONS COLORADO DOLA POPULATION ESTIMATE FROM 2000 TO 2022

FIGURE 2 – WWTF INFLUENT FLOW FROM JUNE 2021 THROUGH MAY 2024

FIGURE 3 – INFLUENT BOD5 CONCENTRATION FROM JUNE 2021 TO MAY 2024

FIGURE 4 – INFLUENT BOD5 LOADING FROM JUNE 2021 TO MAY 2024

FIGURE 5 – INFLUENT TSS CONCENTRATION FROM JUNE 2021 TO MAY 2024

FIGURE 6 – ANNUAL AVERAGE OF BOD5 CONCENTRATION

FIGURE 7 – ANNUAL AVERAGE OF TSS CONCENTRATION

FIGURE 8 – INFLUENT WASTEWATER FLOW PROJECTIONS COMPARED TO CURRENT RATED CAPACITY

FIGURE 9 – INFLUENT FLOW PROJECTIONS COMPARED TO PROPOSED RATED CAPACITY

FIGURE 10 – LOADING PROJECTIONS COMPARED TO PROPOSED ORGANIC CAPACITY

FIGURE 11 – SBR ALTERNATIVE SITE LAYOUT

FIGURE 12 – PROCESS FLOW DIAGRAM FOR AGS

FIGURE 13 – AGS ALTERNATIVE SITE LAYOUT

FIGURE 14 – PROCESS FLOW SCHEMATIC FOR MBR

FIGURE 15 – MBR ALTERNATIVE SITE LAYOUT

FIGURE 16 – DIGESTER IMPROVEMENT SITE LAYOUT

Wastewater Treatment Facility Master Plan v

APPENDICES

APPENDIX A – SUPPORTING DOCUMENTS

APPENDIX B – FIGURES

APPENDIX C – DESIGN CALCULATIONS

APPENDIX D – OPINION OF PROBABLE COSTS

APPENDIX E – OTHER DOCUMENTATION

Wastewater Treatment Facility Master Plan 1

EXECUTIVE SUMMARY

BACKGROUND AND PURPOSE

The Town of Lyons (Town) is located in Boulder County and is approximately 15 miles north of the City of Boulder, Colorado, along US Highway 36. The Town owns and operates an existing wastewater treatment facility (WWTF) located on 2nd Avenue along the St. Vrain Creek jogging path and Kayak Park. The WWTF was originally constructed in 1976 and has been upgraded several times. The original WWTF was replaced in 2014 with the existing WWTF, approved under a Regulation 22 Amendment of Site Location Approval No: ES.12.45343.

The WWTF was approved for a capacity rerating under Site Location Approval Number 4289 in

January 2020 to better reflect the conditions seen at the facility. The existing WWTF is permitted for influent hydraulic and organic loads of 0.3065 million gallons per day (MGD) and 1,535 pounds per day (ppd) of biochemical oxygen demand (BOD5) discharging under CDPS General

Permit COG591156. A previous 2019 JVA Rerating Report and Site Application (2019 Rerating

Report) was developed and submitted to Colorado Department of Public Health and Environment

(CDPHE) to allow for rerating of the Town’s WWTF capacity. The report is included in Appendix

A.

The purpose of this Wastewater Treatment Facility Master Plan (Plan) is to develop a comprehensive planning document to provide guidance for the Town’s wastewater treatment system. This Plan should be viewed as a dynamic working document, reviewed regularly and updated as conditions in the Town’s service area change. The Plan includes historical and projected population data, wastewater flow and loading, and an evaluation of the existing WWTF.

Additionally, this Plan includes a detailed alternative analysis and recommended alternatives for

WWTF improvements.

SCOPE

This Plan is focused primarily on the WWTF itself; it does not provide analysis or recommendations regarding the collection system. The following information will be included in this report:

1. Analysis of Existing Conditions – Discussion of the service area, characterization of historical influent wastewater, description of the WWTF, and a condition and performance assessment of the WWTF process areas.

2. Projected Future Planning Conditions – Projection of future service area growth and associated flow and loading into the WWTF.

3. Alternatives Analysis – Various treatment alternatives to meet the future conditions described in this Plan are presented in this section.

4. Recommended Alternative – Costs and non-quantitative factors are evaluated for each alternative and a recommended alternative is presented.

Wastewater Treatment Facility Master Plan 2

PLANNING PERIOD

The planning period for this report is 20 years, which is consistent with the planning horizon used in Town’s adopted 2023 Comprehensive Plan (Comp Plan), as well as CDPHE requirements for consideration of new or expanded WWTF.

SUMMARY OF TREATMENT ALTERNATIVES

The future conditions used to plan for treatment alternatives can be separated into two main options. Both options suggest reducing the hydraulic capacity of the WWTF in order to accept a higher organic loading capacity. They are summarized in Table 1.

Table 1 – Loading Scenario Summary

Scenario

Hydraulic Capacity

Organic Capacity

Organic Concentration

MGD ppd mg/L

Increased Organic Capacity 0.253 1,900 900

Current Rated Organic Capacity 0.253 1,535 727

Reducing the organic loading to the WWTF should be a top priority as it is one of the primary drivers for significant facility improvements. The loading scenarios presented in Table 1 are considered the worst-case scenario for planning purposes if loading cannot be reduced through managerial methods. Efforts have been made previously to address the high organic loading at the facility, but recent sampling data shows that these efforts have not yet been entirely successful.

For the scenario of increased organic capacity, the treatment technologies evaluated included sequencing batch reactors (SBR), aerobic granular sludge (AGS), and a membrane bioreactor

(MBR). For the scenario that keeps the current rated organic capacity, the recommendation is to implement the aeration changes noted in the 2019 Rerating Report. While the Town’s permit for their current rated organic and hydraulic capacity was approved by CDPHE, they have not yet installed the changes required to meet that organic loading.

In addition to the secondary treatment alternative, the Town requested improvements to their solids stabilization and solids handling systems. The current aerated solids holding tanks (ASHTs) are not sufficiently sized to produce Class B biosolids. The dewatering centrifuge is also undersized.

Digestion improvements and dewatering alternatives (screw vs. rotary fan press) were evaluated as a part of this Plan.

Additionally, there are several improvements to the existing WWTF that are recommended regardless of the selected secondary treatment alternative. These improvements would address the performance limiting factors identified in the existing conditions assessment.

Wastewater Treatment Facility Master Plan 3

RECOMMENDED ALTERNATIVE

It is important to note that the following secondary treatment alternatives are required to address the worst-case loading scenario. As discussed previously, the Town should make reducing the organic loading a top priority. However, for conservative planning purposes, the recommendations in this Plan are based on the worst-case scenario if loading cannot be reduced through managerial methods.

A weighted decision matrix was developed to rank the secondary treatment alternatives. Six categories were included in the decision matrix: Operability, Process Performance, Constructability, Footprint, Capital Cost, and Operations & Maintenance (O&M) Cost. Table 2 shows the score for each secondary alternative based on the six criteria on a scale of one to five

(give being the most favorable) and weighted as shown. The highest priorities for the Town were operability and process performance, with capital cost as the third highest priority.

Table 2 – Decision Matrix for Secondary Treatment Alternatives

Criteria Weight Alternative 1

SBR

Alternative 2

AGS

Alternative 3

MBR

Operability 25% 5 4 3

Process Performance 30% 2 4 5

Constructability 5% 4 3 3

Footprint 15% 2 5 5

Capital Cost 20% 2 3 4

O&M Cost 5% 3 4 2

TOTAL 100% 2.9 3.9 4.1

Note: Scores are on a scale of 1 to 5, with 5 being the most favorable score

The decision matrix indicates that the MBR is the most favored secondary treatment alternatives for the Increased Organic Loading scenario. In addition to the secondary process, there are many other areas of the WWTF that require improvements. The Plan includes a “menu” of potential capital improvement projects, with priorities for Town consideration noted below in Table 3.

Table 3 – WWTF Improvement Options Option Project Total Selection

Preliminary Processes Pick Any Number of Options

IPS Upgrades (Screen) $1,050,000

Wet Well Upsize $560,000

Splitter Box Rehab $120,000 x

Redirect Side Stream Flows $140,000 x

Secondary Treatment Pick One Option

SBR Expansion $9,290,000

AGS Expansion $8,100,000

MBR Expansion $7,310,000 x

Consolidation $20,200,000

SBR Rerating Improvements $1,560,000

(table continues on next page)

Wastewater Treatment Facility Master Plan 4

Option Project Total Selection

Disinfection Pick Any Number of Options

Post EQ Basin Pumps Upgrades $300,000 x

Replace and Upgrade UV System $340,000 x

NPW System Relocate $430,000 x

Digestion Pick One Option

Aerobic Digester Expansion $7,660,000 x

ASHT Upgrades $650,000

Dewatering Pick One Option

Screw Press $880,000 x

Fan Press $1,760,000

Miscellaneous Pick Any Number of Options

Replace Odor Control System $1,040,000 x

New Instrumentation $100,000 x

Backup Generator $210,000 x

Total $18,530,000

The above table indicates which options JVA recommends for the Town based on the existing system condition assessment, discussions with operations staff, and combining priorities into a single project. The recommended improvements have been selected to balance cost and feasibility while positioning the WWTF to best be able to comply with the discharge permit and accommodate any anticipated future flow and loading. For example, although the SBR rerating improvements may be a lower capital cost option for the secondary treatment alternative, the capacity increases gained by these improvements may not be sufficient for a 20-year planning period, and another expansion project may be required within the 20-year planning period. This would result in high capital costs overall compared with implementing a long-term solution now.

The Opinion of Probable Costs (OPC) for the selected improvements is $18.5 million. The OPC breakdown of each option is included in Appendix D. Each of the above recommendations are discussed in more detail in the Plan.

FUNDING OPPORTUNITIES

A multi-funding source approach is recommended to implement the WWTF improvements.

Significant funding amounts, through a combination of grants and low interest loans, may be received from the below funding options.

• Bipartisan Infrastructure Law

• State Revolving Fund – Low Interest Loans

• USDA, Rural Development

• Department of Local Affairs Energy and Mineral Impact Assistance Fund o Administrative Grants o Tier I Grants o Tier II Grants o Community Development Block Grants (CDBG)

• Small Systems Training and Technical Assistance (SSTA) Grants

• Water Quality Improvement Fund (WQIF) Grants

Wastewater Treatment Facility Master Plan 5

• Colorado Water Resources and Power Development Authority Grant Assistance Program

(GAP) for Small Systems

• Colorado Water Conservation Board (CWCB) o Flood and Drought Response Fund o Water Project Loan Program o Colorado Water Plan Grants

A funding approach that uses multiple funding opportunities to maximize grant dollars and low interest loans to mitigate rate increases is recommended. The above funding opportunities are discussed in more detail in Section 6 of the Plan.

Wastewater Treatment Facility Master Plan 6

SECTION 1 – EXISTING CONDITIONS

PLANNING AND SERVICE AREA

The Town’s adopted 2023 Comprehensive Plan (Comp Plan) will be used as a basis for the planning and service area of this Plan. The Comp Plan explains that the Lyons Primary Planning

Area includes the incorporated Town of Lyons, North/South/East St. Vrain subareas, and unincorporated portions of Boulder County adjacent to the Town that are not contained in the above subareas. The Town’s planning area is shown in Appendix B.

The existing service area spans across the Town of Lyons, and currently includes residential, commercial, and industrial customers. The Plan will base projections off the same service area locations, but with the addition of the Eastern Corridor development.

The Comprehensive Plan outlines the community’s growth goals for the next 20 years; the planning period for the Plan will match this time period.

HISTORICAL POPULATION

Historical population estimates for Lyons were obtained from the United States Census (Census) reports and Colorado State Department of Local Affairs (DOLA). Table 4 summarizes these population data sources.

Table 4 – Historical Population from 2000 to 2022

Year

Lyons U.S. Census Data Lyons Colorado DOLA Data

Population Estimate

Annual Growth Rate Population Estimate Annual Growth Rate

2000 1,585

2.25%

1,601 N/A

2001 - 1,642 2.56%

2002 - 1,635 -0.43%

2003 - 1,618 -1.04%

2004 - 1,621 0.19%

2005 - 1,642 1.30%

2006 - 1,774 8.04%

2007 - 1,821 2.65%

2008 - 1,972 8.29%

2009 - 2,005 1.67%

2010 2,033 2,037 1.60%

2011 -

0.83%

2,080 2.11%

2012 - 2,119 1.88%

2013 - 2,146 1.27%

2014 - 2,062 -3.91%

2015 - 2,118 2.72%

2016 - 2,145 1.27%

2017 - 2,158 0.61%

Wastewater Treatment Facility Master Plan 7

Year

Lyons U.S. Census Data Lyons Colorado DOLA Data

Population Estimate

Annual Growth Rate Population Estimate Annual Growth Rate

2018 -

0.83%

2,193 1.62%

2019 - 2,197 0.18%

2020 2,209 2,203 0.27%

2021 - - 2,173 -1.36%

2022 - - 2,145 -1.29%

A graph of the Lyons DOLA population estimate is shown in Figure 1 below. On average, the

Town has experienced relatively moderate growth since 2014.

Figure 1 – Lyons Colorado DOLA Population Estimate from 2000 to 2022

The Town experiences a high transient population tied mostly to restaurant visits that is not reflected in the Census and DOLA population data. Upon discussion with the Town, it was agreed to exclude the transient population from the starting population of the 20-year planning period.

The starting population used for the 20-year planning period is the 2022 DOLA population of

2,145 people.

CURRENT WASTEWATER FLOWS AND LOADS

EXISTING FLOWS

Influent hydraulic flows to the WWTF are reported via Discharge Monitoring Reports (DMRs).

This information is publicly available via the Environmental Protection Agency’s (EPA)

Enforcement and Compliance History Online (ECHO) database. Monthly average flows, as well

1,000

1,200

1,400

1,600

1,800

2,000

2,200

2,400

2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022

P o p u la ti o n

Wastewater Treatment Facility Master Plan 8 as daily maximums, from June 2021 to May 2024 are summarized in Table 5. Flow data is presented in monthly averages and daily maximums as required in the Town’s discharge permit.

Table 5 – WWTF Influent Flow from June 2021 thought May 2024 30 Day Average (MGD) Daily Max (MGD)

Average 0.128 0.181

Maximum 0.201 0.248*

*April 2023 outlier was removed

Flow data at the WWTF is measured by a 6-inch electromagnetic flow meter located on the common discharge pipe of the influent pumps. As seen in Figure 2, the WWTF has not exceeded the permitted 30-day average flow, except instance of a daily maximum flow exceedance in April

2023. The heavy rains seen in the spring of 2023 may have contributed to this abnormally high daily max influent flow, and thus data considered an outlier in the reported flow data. This is also reflected in the increased flow from May to September of 2023 as compared to previous years.

The high flows seen during this time are not considered to be representative of the flow conditions typically seen at the WWTF. Given the current flows conditions, the WWTF is not expected to exceed its permitted capacity of 0.3065 MGD in the 20-year planning period.

Figure 2 – WWTF Influent Flow from June 2021 through May 2024

The average monthly flow from 2021 to 2024 was 0.128 MGD. At the starting population of 2,145 people, this equates to about 60 gallons per capita per day (gpcd). This per capita flow is below the suggested minimum per capita wastewater flow of 75 gpcd as indicated in the Colorado

Department of Public Health and Environment (CDPHE) Wastewater Design Criteria Policy

(WPC-DR-1). The recommended minimum value of 75 gpcd was selected for design purposes;

Wastewater Treatment Facility Master Plan 9 this more conservative estimate helps capture the transient community flow discussed earlier, as well as eliminating the need for additional data collection and explanation to CDPHE to approve a lower per capita flow.

EXISTING LOADING

The historical average organic loading to the WWTF, as measured by BOD5 and total suspended solids (TSS) from June 2021 to May 2024, is summarized in Table 6. The Town’s discharge permit requires that concentration and loading are presented as both monthly averages and the maximum weekly average recorded during that month.

Table 6 – Influent Loading Summary from June 2021 to May 2024

BOD5 Concentration

(mg/L)1

BOD5 Loading (ppd)1

TSS Concentration (mg/L)2

Average (30 Day Average)

513 538 537

Maximum (30 Day Average)

880 881 906

Average (Max 7 Day Average)

692 723 709

Maximum (Max 7 Day Average)

1,371 1,226 1,225

1DMR only has available data from April 2021 to May 2024 2A outliner data point was removed due to an assumed DMR data typo

Figure 3 below shows the influent BOD5 concentrations over the last three years. BOD5 concentrations generally increased over this period.

Figure 3 – Influent BOD5 Concentration from June 2021 to May 2024

Figure 4 below shows the influent BOD5 loading over the last three years. Loading is measured in pounds per day (ppd) and calculated by the multiplication of influent BOD5 concentration and

Wastewater Treatment Facility Master Plan 10 influent flow. Figure 4 shows more BOD5 variability throughout each year, but still shows the overall increasing trend.

Figure 4 – Influent BOD5 Loading from June 2021 to May 2024

As shown in Figure 5, TSS concentrations are more variable than the BOD5 concentrations, but still exhibit a general upward trend. The high 7-day values for both TSS and BOD5 are expected to be due to the high tranient loads seen by Lyons, relating to high tourism times and industrial dischargers.

Wastewater Treatment Facility Master Plan 11

Figure 5 – Influent TSS Concentration from June 2021 to May 2024

The current three-year average for BOD5 and TSS are 513 mg/L and 537 mg/L, respectively. Note that an outlier data point for the maximum 7-day concentration for TSS was removed due to an assumed typo in the DMRs.

The three-year average is not entirely representative of the existing conditions at the WWTF due to the consistently increasing influent values. Figure 6 depicts the annual average BOD5 concentrations for each year, beginning in 2021. Please note that the 2021 and 2024 annual averages in the figures below only include data for half of the year and are not representative of the whole year. As seen in the graph, the DMR concentrations for BOD5 have shown a clear increase annually since 2021.

Wastewater Treatment Facility Master Plan 12

Figure 6 – Annual Average of BOD5 Concentration

The Town has expressed concerns with higher influent BOD5 concentrations to the WWTF, due to both high strength industrial dischargers and water conservation efforts. The current maximum month average monthly BOD is 880 mg/L (occurred March 2023). The current maximum month

7-day BOD5 is 1,371 mg/L (occurred February 2024). To address the Town’s concerns and observed data, the recommended design basis for BOD5 concentration is 900 mg/L. This value is expected to be high enough to capture the current and future conditions due to additional industrial dischargers and reasonable seasonal peaks in max month values.

The 900 mg/L design basis is recognized to be conservative, and represents the worst-case scenario given the current loading seen at the WWTF. Reducing the organic loading to the WWTF should be a top priority as it is one of the primary drivers for significant facility improvements. The secondary treatment alternatives presented in this Plan are considered the worst-case scenario for planning purposes if loading cannot be reduced through managerial methods. Efforts have been made previously to address the high organic loading at the facility, but recent sampling data shows that these efforts have not yet been entirely successful.

Wastewater Treatment Facility Master Plan 13

Figure 7 – Annual Average of TSS Concentration

Figure 7 depicts the annual average TSS concentrations for each year, beginning in 2021. TSS trends are similar to BOD, with a clear increase annually since 2021.

PERMIT COMPLIANCE

The Town has been issued two noncompliance violations since 2021. A summary of the compliance violation is shown in Table 7. The main noncompliance issues were related to effluent violations for E. coli and Nitrogen, ammonia total (as N).

Table 7 – Summary of Permit Violations

Date Reported Violation Percent Exceedance Statistical Type

1/31/2023 Effluent Violation – E. coli 33% Max 7-Day

3/31/2024 Effluent Violation – Nitrogen, ammonia total (as N) 39% Monthly Average

There was only one occurrence of the above noted violations for each constituent. The WWTF has not seen reoccurring violations in the past three years and is in compliance with the discharge permit.

Wastewater Treatment Facility Master Plan 14

SECTION 2 – CONDITION AND PERFORMANCE

ASSESSMENT

EXISTING WASTEWATER TREATMENT FACILITY LAYOUT AND DESCRIPTION

The Town’s WWTF is located on 2nd Avenue along the St. Vrain Creek jogging path and Kayak

Park, located at approximately 40°13’11.352” N and 105°15’50.6088” S. The WWTF was constructed in 1976 and has been upgraded several times. The original facility was replaced in

2014 with a new facility, approved under Regulation 22 Amendment of Site Location Approval

No: ES.12.45343. The WWTF was approved for a capacity rerating in January 2020 and is currently operating under General Permit COG591156.

PRELIMINARY PROCESSES

Wastewater collected in the town is conveyed to the WWTF by an influent pump station (IPS) which is followed by flow metering and Headworks for preliminary treatment. Preliminary treatment processes are discussed in detail in the sections below.

Influent Flow Monitoring

The IPS wastewater flow rate is measured by a 6-inch magnetic flow meter located on common header off the three influent pumps all operated on variable frequency drives (VFDs). Metered influent flow is displayed, monitored, recorded, and logged via local transmitter integrated with the main WWTF programmable logic control (PLC) and Supervisory Control and Data

Acquisition (SCADA) system.

Influent Sampling

The influent sample point is just downstream of the mechanical fine screen. The frequency, constituent, and type of influent sampling is in accordance with the Town’s General Permit. During sampling events, the operation staff set up a refrigerated composite sampler that is hard wired to the main PLC for flow pacing the sample with the influent flow meter over a 24-hour period. The composite sample is removed from the composite sampler and packaged in ice and taken to

Colorado Analytical for testing and analysis.

Headworks Room

The headworks room is rated as Class 1, Division 2 in accordance with NFPA 820. The headworks

HVAC system provides 12 air changes per hour via gas fired make-up air unit integrated with an exhaust fan to maintain this classification. All electrical switchgear for the preliminary treatment equipment is in the separate unclassified MCC-1 / Blower area of the building. The preliminary treatment control panels (screening and grit removal) are fed from the MCC-1 and located in the

Wastewater Treatment Facility Master Plan 15 adjacent mechanical unclassified room separated from the headworks process area. The local control panels communicate with the main WWTF PLC and SCADA system.

Mechanical Screening and Bypass Screen

From the IPS, pumped influent is discharged into a 20-inch-wide influent channel with an automatic inclined 6-mm fine screen with integral washer and compactor. In the event the automatic screen becomes inoperable or taken down for maintenance, there is a bypass channel in-line with a 1-inch manual bar screen. Flow can be diverted with the use of stop plates and overflow weirs. Under normal conditions, the influent is screened by the automatic mechanical screen. The screen washes, compacts, and bags screenings prior to discharge into a dumpster. Screenings that accumulate on the manual screen are manually removed, placed on a beach plate, and allowed to dewater prior to placing the screenings in the dumpster.

Grit Removal

A vortexing grit chamber removes grit from the raw influent wastewater. Wastewater tangentially enters the grit chamber to help induce a vortex within the chamber. A small hydraulic jet nozzle is used to further impart tangential vortex velocity and increase grit particle settling efficiency.

Additionally, a small regenerative blower is used to diffuse air within the basin and aid in removal of particulates. A submersible grit pump installed in the grit hopper pumps accumulated grit slurry to a hydro cyclone mounted on the top of a grit classifier. The hydro cyclone concentrates the grit slurry and separates the water from the grit particles. Grit separated wastewater from the hydro cyclone and grit classifier is drained by gravity back to the influent channel. Washed and dewatered grit is augured to the discharge of the classification equipment via an inclined screw. The discharge of the classifier is fitted with a continuous bagging attachment that bags the classified grit prior to being placed in a dumpster for landfill disposal.

Scum Removal and Splitter Box

Following preliminary treatment, influent flows by gravity to a splitter box where it can be diverted to one or both ICEAS™ Sequencing Batch Reactors (SBRs) using weir plates that are installed behind an underflow baffle that is designed to keep scum and floatables out of the downstream

SBR basins. The scum flows over a weir plate and enters a pipe that directly discharges into an aerated sludge holding tank.

SECONDARY TREATMENT

Following preliminary treatment, wastewater is split between two Sequencing Batch Reactor

(SBR) basins. The SBR process provides compact, continuous flow biological treatment of the wastewater to achieve high levels of carbonaceous (BOD5) and nutrient removal of highly variable flows and loads. The SBR system is manufactured by Sanitaire Intermittent Cycle Extended

Aeration (ICEAS™) Advanced SBR system, which uses two process reactors in parallel to biologically treat wastewater and discharge high-quality effluent. The ICEAS SBR is a continuous flow system with react, settle and decant phases; it consists of a pre-react zone and a main aeration zone. All basins are monitored by an oxygen reduction potential (ORP) probe and dissolved

Wastewater Treatment Facility Master Plan 16 oxygen (DO) probe, respectively. The main react zone cycles air on and off during the react phase to provide favorable conditions for simultaneous nitrification/denitrification, thereby reducing energy costs. A submersible mixer located in the main zone runs continuously during the react phase and is off during the settle and decant phases.

SBR Aeration and Mixing

The ICEAS process uses fine bubble membrane diffusers to provide oxygen to the pre-react zone and main zone. Air to the diffuser grids is supplied by three (two duty and one swing) screw compressor (hybrid) 20 HP blowers capable of 250 standard cubic feet per minute (scfm). They are located in the operations building. The intent of the diffused air in the pre-react zone is to provide just enough air for mixing and to maintain a low DO environment to enhance denitrification. The main zone also includes a submersible mixer that runs continuously during the react phase with on-off aeration to facilitate simultaneous nitrification/denitrification. The operation of the blowers is automatically controlled by the WWTF’s control system via a combination of adjustable timers and online monitoring.

Effluent Equalization

An effluent equalization (EQ) tank is provided to allow the SBR tanks to decant secondary treated effluent and prepare for the next batch, as well as to reduce the peak flow and provide a steady flow rate to the disinfection system. Effluent equalization is common in SBR systems because decanting rates are typically much higher than the average design flow rate. The equalization tank is sized for the peak 2.4-hour cycle flow rate which is equivalent to a peak hour flow of 1.0 MGD.

The decant phase that occurs during the peak cycle has a duration of 36 minutes and an associated decant flow rate of 1,411 gpm, resulting in a decanted volume of 50,800 gallons. The equalization process captures and retains the decanted effluent, then pumps the effluent at a constant rate to the ultraviolet (UV) disinfection channel until the low-level setting of the tank is met and decant cycle process repeats for each cycle.

Alkalinity Adjustment

To maintain sufficient alkalinity for nitrification, liquid magnesium hydroxide (MgOH) is dosed into the SBR influent splitter box. The liquid MgOH dosing system consists of 55-gallon drums storage and peristaltic chemical metering pumps that are integrated to the PLC and paced off the influent flow meter.

DISINFECTION AND NON-POTABLE WATER SYSTEM

UV light is used to disinfect the secondary effluent prior to discharge to St. Vrain Creek. The UV system can achieve pathogen inactivation to comply with the effluent permit limits for E. coli. The disinfection system has sufficient hydraulic capacity to effectively treat the peak daily flow rate from the equalization basins for up to 0.6 MGD. The system is designed to meet an effluent E. coli effluent limit of 3,108 / 100 ml on a 7-day geometric mean, and an effluent E. coli limit of 1,441 /

100 ml on a 30-day geometric mean.

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The Trojan 3000 PTP UV system is a horizontal lamp system with low pressure lamps oriented parallel to the effluent flow. The system is capable of modulating lamp intensity to provide sufficient disinfection based on effluent flow rate and transmittance. A manual lamp sleeve cleaning station is provided in the UV room which allows for mechanical and chemical cleaning of the quartz sleeves. When cleaning or replacement of a module is necessary, each module can be individually removed from the UV bank and the spare module inserted in its place while the bank remains in operation. To provide an indication of fouling, excessive effluent turbidity, or lamp age, a submersible UV sensor is mounted to one module within the bank to measure UV intensity.

SBR decant effluent flow is pumped into the channel upstream of the UV banks and then through the UV banks for disinfection. A serpentine weir at the effluent end of the UV channel maintains a constant level through the UV banks to allow for full submergence of the lamps and prevent short circuiting. Two UV banks in series provide treatment of the peak daily flow (PDF) rate of

0.6 MGD. A single bank is capable of disinfecting at the maximum month flow rate of 0.38 MGD.

Emergency backup power is supplied to the UV system in the event of a power outage.

At the effluent end of the UV channel contains a small storage basin integral with the UV channel.

Disinfected effluent is pulled from the basin for non-potable water (NPW) use. A single 7.5 NPW vertical turbine centrifugal pump supplies the NPW needs for the screening, grit classifier, dewatering, and odor control. The pump is operated off a VFD and hydro-pneumatic tank to maintain a set pressure range for the NPW system.

SOLIDS HANDLING

The solids handling system consists of two submersible waste activated sludge (WAS) pumps (one for each SBR), two aerated sludge holding tanks (ASHT), two submersible sludge transfer pumps

(one for each ASHT), a sludge balancing tank, one centrifuge feed pump, a polymer feed system, and a single centrifuge.

The operators set a WAS pump time interval for pumping wasting sludge to the ASHT to maintain a targeted MLSS concentration in the SBRs. WAS can be pumped to either ASHT and the ASHTs can be operated in series or parallel. ASHT #1 is equipped with a floating decanter pump system to pump clear liquid back to the IPS. ASHT #2 uses a telescoping valve to decant clear liquid back to the IPS. Supply air to the ASHTs is valved off the main air header for the SBRs and metered with thermal mass flow meters monitored via WWTF PLC and SCADA. After decanting, the thickened biomass from the holding tank is pumped to a solids balancing tank via a submersible solids transfer pump. The biosolids in the solids balancing tank are then pumped by a positive displacement feed pump, blended with activated emulsion polymer and delivered to the centrifuge.

The dewatered cake concentration ranges from 14 to 17 percent solids. The dewatered cake produced from the centrifuge is discharged into a dumpster and then hauled off for contract disposal or processing.

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ODOR CONTROL

Foul air generated from specific areas of the facility are ducted to a synthetic media bio trickling treatment process for treating organic and inorganic odor compounds. The odor control equipment receives foul air from the following sources: Influent lift station wetwell, space under screening channel covers in the headworks area, aerated sludge holding tanks, and the solids processing area.

The requirements of the National Fire Protection Act (NFPA) Code and CDPHE regulations provide that an odor control design will, at a minimum, provide a safe working environment for personnel and minimize off site odors that negatively affect those persons located in proximity to the WWTF, and satisfy NFPA ventilation requirements for specific process areas.

The bio trickling synthetic media is used in conjunction with non-potable water to scrub the generated foul air. Foul air ducts push the foul air through the bottom of the filter as water is filtered through the top to facilitate growth of autotrophic and heterotrophic bacteria. The biofilter tank and foul air fans are located outdoors on a concrete equipment pad. Channel covers, wetwell covers, and enclosed rooms contain the odors and prevent fugitive odor from escaping these areas.

The odor control system fans maintain a constant vacuum to further prevent fugitive odors from escaping.

POWER AND CONTROLS

The WWTF currently has two utility power sources available to it provided by the Town of Lyons

(Primary) and City of Longmont (Backup). These power sources are fed into an Automatic

Transfer Switch (ATS) to coordinate changeover to backup power.

Instrumentation was observed to be provided by reputable manufacturers. These consist of

Rosemount for the Magnetic Flow Meters, Dissolved Oxygen and ORP by YSI, Endress & Hauser for level measurement, and others. Controls consist of multiple control panels including the

Influent Pump Station (LCP-1000), Headworks (LCP-2000), among others. IPS is controlled by three wall mounted VFDs while other motor starters are in the MCC located in the main process building.

PERFORMANCE ASSESSMENT AND LIMITING FACTORS

PRELIMINARY PROCESSES

Condition and Performance Assessment

The IPS and preliminary treatment equipment is in good condition and is well maintained. No noticeable degree of concrete degradation was observed for the influent wet well and the headworks open channels. There is no mechanical screening prior to the IPS. As such, the influent pump station requires frequent cleaning to remove accumulated material and to minimize the pumps from clogging.

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Performance Limiting Factors

The influent pump wet well is undersized for current operations and results in more frequent on/off influent pumping. The capacity of the pumps and VFDs is also limited for the system.

SECONDARY TREATMENT

Condition and Performance Assessment

The secondary treatment process equipment is in good condition and well maintained. The SBR membrane fine bubble diffusers are nearing the end of their useful life and should be replaced soon.

The splitter box is not equally distributing the influent flow to the SBR basins resulting in one basin getting more flows. The south SBR basin is the one getting a higher percentage of influent flow and loading. This results in less efficient treatment performance of the south SBR and requires a greater volume of WAS to be pumped out (compared to the north SBR) due to higher yield.

Side stream flows from the ASHTs decant and the centrate from the centrifuge is conveyed back to the IPS wet well which is before the influent sampling point resulting in a higher influent TSS, BOD5, and nutrient loading. Operations staff must coordinate decant/dewatering with influent sampling.

The post equalization pumps run in an ON / OFF configuration and do not have VFDs, resulting in variable flows to the UV system due to changes in level of the post equalization tank.

Performance Limiting Factors

The capacity of the two SBR basins are not fully utilized due to the unequal split of flows. This lowers the overall treatment capacity of the WWTF and ability to accommodate a higher flow and loading future conditions.

Each of the existing blowers are sized for 250 standard cubic feet per minute (SCFM) at 8.5 pounds per square inch (psi). Previous modeling efforts in the 2019 Rerating Report and approved 2020

Site Application have shown that the blowers are insufficiently sized for the current permitted capacity.

DISINFECTION

Condition and Performance Assessment

The existing UV system is aging and reaching the end of its useful life. Due to the age of the system, Trojan no longer supports some of the replacements parts. The UV system has very simplified controls making it more challenging for operators to diagnose lamp outages and ballast failures. The UV system is designed for ON / OFF operation meaning that lamps will turn on at full wattage and are not capable of varying UV intensity based on flow rate. The UV lamps are cleaned manually and not fitted with an automatic wiper system.

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The NPW pump suction pipe is connected to the effluent end of the UV channel which is not adequately sized for the non-potable process needs of the WWTF. The volume of NPW storage is approximately 50 gallons and does not contain enough volume for the NPW supply system. Post

SBR EQ pumping is intermittent, meaning that the non-potable pumps run out of supply water in a very short period. This causes major operational issues and results in the use of potable water for all non-potable uses.

The UV system lacks adequate diagnostics and alarm systems, and operators have reported encountering difficulty obtaining replacement parts in a timely manner. The ON / OFF operation of the UV system results in higher energy usage and shorter lifetime for the UV lamps.

SOLIDS HANDLING

Condition and Performance Assessment

During the operation of the centrifuge, it was observed that the capture efficiency was very poor resulting in approximately 45 to 50 percent of the solids being returned back to the head of the

WWTF, resulting in additional solids loading to the SBR process.

The centrifuge is undersized and inefficient, resulting in poor solids capture. When the centrifuge is meeting operational requirements, cake is hauled by McDonald Farms twice per week. The dewatered biosolids do not meet Class B requirements under the Environmental Protection Agency

(EPA) Part 503 Biosolids Rule and have to be hauled to a composting site for further processing.

The frequent hauling of solids and additional disposal process results in increased costs.

The waste activated sludge (WAS) pumps are oversized, as they were originally designed for return activated sludge (RAS) pumping at the facility. The oversized pumps have led to operational challenges, including the potential for overwasting sludge from the SBRs, which disrupts the ability to maintain the desired mixed liquor suspended solids (MLSS) levels and impacts the efficiency of the secondary treatment system. Additionally, overwasting sludge with the WAS pumps is overloading the already undersized Aerated Solids Holding Tanks (ASHTs) and causing more frequent pump start and stops. This results in increased wear and tear on the pumps.

ASHT #1 contains a telescoping valve with 9-inches of travel for decanting. The travel distance of the valve is insufficient for effective decanting of supernatant. The operators do not use the telescoping valve for this reason. ASHT #2 was upgraded using a submersible pump with an electronic eye for decanting which has improved solids thickening inside ASHT #2, however operators have had issues of over decanting into the sludge blanket, resulting in higher solids loading being returned to the IPS.

Performance Limiting Factors

The centrifuge is undersized and is inefficient at times with poor capture efficiency. The centrifuge operates 5 days a week, 8 hours a day, which is cumbersome for operation staff and time

Wastewater Treatment Facility Master Plan 21 consuming to monitor and clean. If the centrifuge is taken down for maintenance or repairs, liquid sludge from the ASHTs is hauled off for composting, which is very costly and time consuming.

The ASHTs tanks are currently significantly undersized. The total volume of the two basins is roughly 118,000 gallons. With some assumptions on solids concentration and influent loading, the required volume to achieve Class B biosolids is anywhere between 350,000 and 530,000 gallons.

Additionally, to be considered an aerobic digester by CDPHE, the depth must be a minimum of

10 feet; the existing tanks are 9 feet deep.

The tanks also share air with the SBRs, meaning they do not receive enough air to meet Class B.

The existing 3 blowers can generate 750 scfm total, while the digesters alone would require a minimum of 800 scfm to function effectively.

ODOR CONTROL

Condition and Performance Assessment

The Bioair odor control unit has been taken offline and is currently not functioning. Further evaluation is necessary to determine the reasons why the odor control unit is not operating and performing. Operators are dosing an organic additive to the ASHTs for controlling odors. Minimal improvement has been observed to date using this additive.

Performance Limiting Factors

The odor control system is not operating, resulting in odors inside the WWTF and its outside boundaries.

POWER AND CONTROLS

Condition and Performance Assessment

Instrumentation interior to structures appears to be in good, working condition. Any instrumentation and panels exterior to the structure has sustained sun damage and appears to be in less than satisfactory condition. The age of the instrumentation is approximately 10 years old and at the end of its useful lifetime. Replacement parts and instruments of the same vintage will become more difficult to obtain due to discontinuation of representing manufacturers.

For the SCADA system, Inductive Automation Ignition is installed in the facility but does not appear to have been programmed properly to achieve maximum functionality. For example, the

IPS control panel does not have an active connection to the main Ignition gateway. Therefore, no remote-control functionality is available for the IPS.

The WWTF currently has two utility power sources, with the ATS to coordinate changeover to backup power. The Town and operations staff has stated that they have had issues with losing a phase of power and damaging equipment with no change-over to backup power. It is believed that this ATS may not have been programmed correctly as this issue should not occur.

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Electrical gear and instrumentation that is approaching end of life can operate inefficiently and have inaccuracy as well. Though the SCADA software is adequate, the lack of a properly programmed SCADA system can cause operational issues for the staff such as state reporting and general control. The likely poor design and programming for the ATS utilizing two utility power feeds has caused dropped power issues with the facility.

FLOODPLAIN ISSUES

The Town has adopted the Boulder County Colorado Hazard Mapping Program (CHAMP) floodplain maps that will update the current Federal Emergency Management Agency’s (FEMA’s) floodplain mapping in Fall 2024. The updated Boulder County CHAMP mapping locates the

Town’s WWTF in the 500-year floodplain of the St. Vrain Creek floodplain, as seen in the updated map in Appendix B.

Any alternatives that require new or expanded buildings should be designed to be located within the 500-year floodplain boundary. Any new infrastructure that is located in the regulatory floodway would require considerable civil engineering design and permitting efforts.

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SECTION 3 – FUTURE CONDITIONS

POPULATION AND LAND USE PROJECTIONS

The Town’s adopted 2023 Comp Plan and a January 2024 final draft of the Housing Future Plans provide more insight into the Town’s goals, aspirations, and future development plans. These two documents detail the Town’s current and future population and land use plans. Within those two documents, the following growth rates were determined:

• Low Growth = 0.8% (Comp Plan)

• Medium Growth = 0.8% until 2030, then 1.2% until end of planning period (from Comp and Housing Futures Plan)

• High Growth = 1.4% (Comp Plan)

All three growth rate scenarios will be used to project future population, flow, and loading to provide a holistic view on future conditions. However, for planning and design basis purposes, the medium growth of 0.8% until 2030, then 1.2% until the end of the planning period was selected as the basis for projections to discuss proposed alternatives and improvements.

A population projection for each of the three growth scenarios was calculated for the 20-year planning period and is summarized in Table 8.

Table 8 – Population Projection

Year Low Growth (0.8%) Medium Growth (0.8% →

1.2%) High Growth (1.4%)

2022 2,145 2,145 2,145

2023 2,162 2,162 2,175

2024 2,179 2,179 2,205

2025 2,197 2,197 2,236

2026 2,214 2,214 2,268

2027 2,232 2,232 2,299

2028 2,250 2,250 2,332

2029 2,268 2,268 2,364

2030 2,286 2,286 2,397

2031 2,304 2,314 2,431

2032 2,323 2,341 2,465

2033 2,341 2,369 2,499

2034 2,360 2,398 2,534

2035 2,379 2,427 2,570

2036…