3_DRAFT WFP Executive Summary_220103.pdf

Clackamas Water Environment Services

Willamette Facilities Plan

Executive Summary

Draft

Carollo

January 2022

INTRODUCTION

Scope and Purpose

Clackamas Water Environment Services (WES, District) has completed a 20-year planning process for its wastewater treatment facilities that discharge to the Willamette River. This Willamette Facilities Plan

(WFP, Plan) identifies improvements needed to provide capacity for growth, address aging infrastructure, and protect human health and the environment by meeting regulatory requirements through the year 2040. The Plan complies with the Oregon Administrative Rule (OAR) and guidance issued by the State of Oregon Department of Environmental Quality (DEQ). Such compliance facilitates agency approval of the Plan and allows the District to fund necessary projects with low-interest construction loans administered through the Clean Water State Revolving Fund (SRF) program.

Recommended improvements presented in the Plan are based on an evaluation of regional alternatives that consider the District’s Kellogg Creek and Tri-City Water Resource Recovery Facilities (WRRF), as well as wastewater collection and conveyance facilities located throughout the District’s service area. This comprehensive, regional approach allows the District to:

Identify the best use of its wastewater collection, conveyance, and treatment infrastructure;

Develop a prioritized Capital Improvement Program (CIP) to addresses current needs while preparing for potential future requirements;

Implement sustainable, affordable solutions that support economic development; and

Continue to protect Willamette River water quality now and into the future.

Planning Area Definition

The WFP focuses on two distinct areas of service within the District, as shown in Figure 1. These include the Kellogg Creek Service Area, which collects and conveys wastewater for treatment at the Kellogg

Creek WRRF, and the Tri-City Service Area, which collects and conveys wastewater to the Tri-City WRRF.

The two service areas are interconnected at key locations, allowing the District to route wastewater from the Kellogg Creek service area to Tri-City to optimize the capacity and performance of the entire system.

Figure 1 – WFP Planning Area

WASTEWATER FLOWS AND LOADS

Planning Area Population

Determining current and future population numbers within the District’s service areas is a key initial step in the planning process. Consistent with OAR and DEQ guidance, the WFP is based on 2016 population estimates (Population Forecasts for Clackamas County Service Districts, August 2016), in conjunction with Portland State University’s Population Research Center certified population estimates and the 2018 Oregon Metro Regional Transportation Plan.

Table 1 summarizes the planning area population projections through the year 2040. Overall, WES’s service area population is expected to increase by approximately 33 percent, with 64 percent of the growth occurring in areas served by the Kellogg Creek WRRF, and 36 percent of the growth occurring in the Tri-City Service Area. Figures 2 and 3 illustrate more specifically where growth is expected to occur within each service area.

Flow and Load Projections

Estimating the quantity of wastewater that will be generated as population grows is also an essential planning step. Daily wastewater flow (the volume of wastewater generated per day, represented in millions of gallons per day, or mgd) and load (the pounds of material contained within that wastewater volume, represented in pounds per day, or ppd) are each important. With respect to pollutant loads, biochemical oxygen demand (BOD) and carbonaceous BOD (cBOD) – which measure organic material – and total suspended solids (TSS) – which measures solid material – are two key parameters.

Key Design Criteria

The ability to provide reliable, effective conveyance and treatment of wastewater is determined by flow and/or load criteria, depending on the type of process being evaluated. Facility capacities documented in this Plan are based on industry-standard design criteria and are briefly summarized in Table 2 below.

Table 2 – Key WFP Flow and Load Criteria

Type of Wastewater Process Applicable Criteria

Wastewater Conveyance (e.g., pipelines, pumping stations)

Peak Hour Flow (mgd)

Liquid Stream Wastewater Treatment (e.g., screening, settling, biological process)

Avg, Max Month, and Peak Hour Flow (mgd)

Avg, Max Month, and Max Week Load (ppd)

Solid Stream Wastewater Treatment (e.g., thickening, digestion, dewatering)

Avg, Max Month, and Max Week Load (ppd)

Seasonal Flow Considerations

In rainy climates such as the Pacific Northwest, a strong relationship exists between precipitation and wastewater flow. This is due to rainwater entering the sewer system, either through direct connections

(known as “inflow”) or as groundwater flowing through leaky pipes (known as “infiltration”). As a result, the amount of flow from a given service area can vary substantially throughout the year. To capture this variation, the Plan includes flow and load estimates for both “dry weather” (May through October) and

“wet weather” (November through April) seasons. Through a separate but related planning effort

(Collection System Master Plan, Jacobs, 2019) WES has evaluated ways to reduce infiltration and inflow

(I/I). The Collection System Master Plan recommendation of reducing I/I by 65 percent in 19 key basis is the basis for the maximum and peak flow values presented in this Plan.

Current and Projected Values

Flow and load projections for the areas serving the Kellogg Creek and Tri-City WRRFs are combined and shown in Figures 4 and 5, respectively.

Average Dry Season Flow (mgd)

Max Month Wet Season Flow (mgd)

Peak Hour Wet Season Flow (mgd)

Fl o w m gd

Current and Future Flow Projections

2018 2040 Buildout

20,000

40,000

60,000

80,000

100,000

120,000

140,000

Avg BOD (ppd)

Max Month BOD (ppd)

Max Week BOD (ppd)

Avg TSS (ppd)

Max Month TSS (ppd)

Max Week TSS (ppd)

Lo ad p p d

Current and Future Load Projections

2018 2040 Buildout

REGULATORY CONSIDERATIONS

Existing Permit Limits

The WFP evaluates the ability of WES’s existing wastewater facilities to meet current as well as potential future water quality permit requirements. These requirements are included in the Kellogg Creek and Tri-

City WRRF National Pollution Discharge Elimination System (NPDES) Permits, summarized in Tables 3 and 4. Both permits include two distinct seasons to determine regulatory compliance:

Dry Weather Season: During the regulatory dry weather season from May through October, effluent limits in WES’s NPDES Permits are established at more stringent levels, protecting water quality when low streamflow and high temperature conditions exist in the Willamette River.

Wet Weather Season: Conversely, during the regulatory wet weather season, Willamette River streamflow increases and temperatures cool. Less stringent effluent limits are needed to protect water quality during these times.

Because it is very difficult to maintain the highest degrees of treatment when wastewater flows become elevated by storm events, such a seasonal approach protects water quality in an affordable, sustainable manner. This Plan assumes the seasonal approach to permitting will continue in the future.

Future Permit Considerations

Throughout the planning process, WES maintained a high degree of communication and close coordination with Oregon DEQ. This allowed the planning team to make reasonable assumptions with respect to potential regulatory limits that may be included in future NPDES Permits for the Kellogg Creek and/or Tri-City WRRFs. A summary of the regulatory assumptions that were used to guide the analysis of regional and plant-specific alternatives in the WFP is presented in Table 5:

Kellogg Creek NPDES Permit Assumptions Tri-City Permit Assumptions

BOD/cBOD/TSS Concentration Limits

The current permit is not based on the basin standard for technology-based limits for BOD and TSS; however, since the recommended improvements will not change the liquid-stream capacity, no change should be made.

The current permit is based on the basin standard for technology-based limits for BOD and TSS, and no change to this standard should be made.

However, DEQ has implemented a new policy to reduce the CBOD5 limit to be equivalent to the BOD5 limit in the basin standard. This will reduce the monthly CBOD5 average limit to 8 mg/L and the weekly limit to 13 mg/L.

BOD/cBOD/TSS Mass Load Limits

The requirement to meet daily BOD and TSS mass load limits is not currently suspended during peak flow conditions. In the future, WES believes these mass load limits should be suspended on any day that flow exceeds the hydraulic capacity of the secondary treatment process, or 18 mgd.

An alternative approach to suspending the mass load limits would be to establish new daily load limits according to OAR 240-041-0061 (9)(b), which requires the highest and best practical treatment to minimize the discharge of pollutants.

The requirement to meet daily BOD and TSS mass load limits is currently suspended during peak flow conditions. In the future, WES believes these mass load limits should continue to be suspended on any day that flow exceeds two times the average daily flow.

An alternative approach to suspending the mass load limits would be to establish new daily load limits according to OAR 240-041-0061 (9)(b), which requires the highest and best practical treatment to minimize the discharge of pollutants.

As growth continues over time, additional wet weather flow must be transferred from Kellogg Creek to Tri-City. Accordingly, wet weather BOD and TSS mass loads will also increase. WES completed extensive modeling during the planning process to demonstrate that this transfer of load will not impact water quality.

Ammonia Limits

An interim ammonia limit was included in the existing NPDES permit. However, with improved mixing at the Kellogg Creek outfall, the ammonia limit is no longer warranted; therefore it should be removed from future permits.

There is no ammonia limit in the existing permit, and no ammonia limit is required/warranted in future permits. Additionally, a new outfall and diffuser are planned that will improve mixing.

Effluent Toxicity

Modeling was completed to demonstrate no reasonable potential to violate water quality standards at the edge of the outfall mixing zones.

Modeling was completed to demonstrate no reasonable potential to violate water quality standards at the edge of the outfall mixing zones.

Temperature

A mass balance shows there is room for approximately 50 percent growth within the existing thermal load allocation.

A mass balance shows there is room for approximately 30 percent growth within the existing thermal load allocation.

EXISTING WRRF CONDITION

The condition of existing treatment facilities must be well understood in order to develop a 20-year CIP.

This allows for the inclusion and scheduling of projects to rehabilitate or replace components of the existing WRRF that naturally wear-out over time. Such projects are known as “R&R Projects.” As part of the WFP, an extensive condition assessment was conducted by a team of mechanical, structural, and electrical/instrumentation engineers. This team identified the need for R&R Projects based on comprehensive assessment of virtually every structural, mechanical, electrical, and instrumentation component (or “asset”) comprising WES’s wastewater pumping and treatment and infrastructure. Table

6 summarizes the scoring system developed by WES’s team.

Condition Score Description

(Best)

Excellent: Very little wear. Fully operable, well maintained, and consistent with current standards. No further action required.

Good: Sound and well maintained but showing slight signs of wear. Able to deliver full efficiency with little or no performance deterioration. Minor rehabilitation may be needed.

Moderate: Functionally sound but showing normal wear. Minor failures or diminished efficiency/ performance causing increased maintenance. Moderate rehabilitation needed.

Poor: Functional but requiring a high level of maintenance to remain operational. Likely to cause reduce performance in the near term. Major rehabilitation or replacement needed.

(Worst)

Very Poor: Useful life has been exceeded and/or excessive maintenance cost are needed to remain in operation and reduce risk of breakdown. Immediate replacement required.

Kellogg Creek and Tri-City WRRF Condition Summary

Overall, the condition of the Kellogg Creek and Tri-City WRRFs is sound, with the majority of assets scoring 3 or better. However, several assets at both facilities will require substantial refurbishment or replacement over the next decade. The timing and magnitude of recommended R&R Projects for the

Kellogg Creek and Tri-City WRRFs are shown in Figures 6 and 7, respectively.

$1.3

$5.3

$1.6

$1.4

$0.7

$0.9

$0

$2

$4

$6

$8

0 to 2 Years 3 to 5 Years 6 to 10 Years

Es ti m at d C o st

M

Kellogg Creek WRRF R&R Project Costs

Rehabilitate Replace

$5.9

$3.3 $2.2

$1.5

$0.9 $2.6

$0

$2

$4

$6

$8

0 to 2 Years 3 to 5 Years 6 to 10 Years

Es ti m at d C o st

M

Tri-City WRRF R&R Project Costs

Rehabilitate Replace

EXISTING WRRF CAPACITY

The capacity of existing wastewater conveyance and treatment infrastructure must also be defined to identify projects needed to accommodate future growth. Expansion projects for WES’s conveyance infrastructure were identified previously (Collection System Master Plan, Jacobs, 2019). This Plan focuses on identifying expansion projects needed to address capacity deficiencies at the Kellogg Creek and Tri-

City WRRFs. Projects to address both liquid stream capacity (i.e., the ability of facilities to treat wastewater flow), and solid stream capacity (i.e., the ability of the facilities to process the solids contained in the wastewater) are identified.

Kellogg Creek WRRF Capacity

Liquid Stream Capacity

Under existing NPDES permit limits, the existing Kellogg Creek WRRF has sufficient capacity to treat current and projected flows during most of the year. However, WRRF treatment capacity is capped at 25 mgd. Because peak flows in the Kellogg Creek service area currently exceed 25 mgd during large storm events, excess flow is transferred to the Tri-City WRRF. This practice will continue and will become more frequent due to growth in the Kellogg Creek service area. Figure 8 summarizes the liquid stream capacity analysis at the Kellogg Creek WRRF.

Solid Stream Capacity

The “relative capacity” (i.e., the required capacity divided by the available capacity) of the major Kellogg

Creek solids stream treatment processes is shown in Figure 9. Values greater than 1 indicate the need for additional capacity. As shown, improvements to increase the capacity of solids thickening and digestion are required within the planning period. Dewatering, improvements are also needed to eliminate the current practice of hauling solids from Kellogg Creek to Tri-City for dewatering.

Preliminary Primary Secondary Disinfection

Fl o w m gd

Treatment Process

Kellog Creek WRRF Liquid Stream Capacity Available Required (Current) Required (Future)

(1) Flow in excess of available capacity transferred to Tri-City WRRF

(1) (1)

(1)

(1)

Commented [BM1]: Yes, we didn’t use this simplified approach in the TMs. It is difficult to solids show all on one axis, but I will work with Anne to try and come up with a common chart for solids.

Tri-City WRRF Capacity

Liquid Stream Capacity

Figure 10 summarizes the liquid stream capacity analysis at the Tri-City WRRF under existing NPDES permit limits. As shown in the figure, multiple liquid stream processes have reached their capacity to treat peak flow. To address this limitation, the WFP focuses on alternatives that would increase the peak flow hydraulic capacity of the Tri-City WRRF from 72 mgd to 105 mgd within the next several years.

Solid Stream Capacity

The “relative capacity” of the major Tri-City solids stream treatment processes is shown in Figure 11. As shown in the figure, the existing solids handling processes at Tri-City each have adequate capacity;

therefore, solids capacity expansion is not required in the near-term. Depending on several factors, the available capacity of the existing solids thickening process may be exceeded near the end of the 20-year planning period. To be conservative, a project to increase thickening capacity around the year 2040 is therefore included in the WFP.

Thickening Digestion DewateringR e q u ir e d

A va ila b le C ap ac it y

Treatment Process

Kellog Creek WRRF Solid Stream Capacity Available Required (Current) Required (Future)

(1) Solids are currently hauled to Tri-City WRRF for dewatering.

(1)

Preliminary Primary Secondary Disinfection

Fl o w m gd

Treatment Process

Tri-City WRRF Liquid Stream Capacity Available Required (Current) Required (Future)

(1) Flow exceeding secondary capacity treated through Select Treat

(1)

Thickening Digestion DewateringR e q u ir e d

A va ila b le C ap ac it y

Treatment Process

Tri-City WRRF Solid Stream Capacity Available Required (Current) Required (Future)

(1) Thickening improvements eliminate the need for digester expansion.

BASIN-WIDE SCENARIO ANLAYSIS

With the foundational elements of the Plan established, the planning team evaluated a number of basin-wide scenarios to answer several questions, including:

1. During the wet weather season: Should peak flows be treated and discharged at a remote facility located at the Blue Heron property on the West side of the Willamette River, or conveyed to the Tri-City WRRF for treatment and discharge?

2. During the dry weather season: If regulatory requirements become more stringent in the future, what combination of Kellogg Creek and Tri-City WRRF capacity provides the most cost effective means of protecting Willamette River water quality?

Basin-Wide Scenario Considerations and Recommendations

An extensive analysis was completed to compare different basin-wide scenarios based on their capital cost as well as non-cost factors that are consistent with WES’s mission and objectives, considering the following factors.

Capital Cost (Construction + Allied Costs)

Operational Complexity

Water Quality

NPDES Permitting Challenges

Environmental/Land Use Challenges

Community Benefit/Impact

Significant outcomes of the basin-wide scenario evaluation are summarized below:

Providing Peak Flow Treatment During the Wet Weather Season

Conveying peak wet weather flows to the Tri-City WRRF for treatment and discharge is the recommended approach. The estimated capital cost of this approach is very close to the cost of other approaches and expanding the Tri-City WRRF offers several non-cost advantages, including reduced operational complexity and fewer permitting challenges.

Meeting Potential Future Permit Requirements During the Dry Weather Season

If future NPDES permits further restrict oxygen-demanding substances being discharged to the

Willamette River, modifying the existing Tri-City WRRF to achieve these limits is the recommended. This means that liquid stream biological treatment improvements will not likely be needed at the Kellogg

Creek WRRF. However, space to modify the treatment process at the Kellogg Creek site should be retained in case this ever changes.

Taking a basin-wide approach makes the best use of land available for process expansion at Tri-City while preserving the valuable, “conventional” treatment capacity at Kellogg Creek. Regulatory compliance may require a watershed (or “bubble”) NPDES permit that is based on water quality modeling. Similar permits have been developed used before to measure compliance at other treatment facilities in Oregon, and has WES initiated water quality modeling to support this approach as part of the

WFP.

RECOMMENDED PLAN – KELLOGG CREEK WRRF

The planning team completed a detailed facilities plan for the Kellogg Creek WRRF, based on the basin-wide recommendation and prior analyses of flows, loads, capacity, condition, and water quality regulations. Table 8 summarizes projects that are recommended to be completed within the planning period.

Project Description Estimated Capital Cost

1. Disinfection Replace existing disinfection equipment that has reached the end of its useful life with new, reliable disinfection equipment.

$2.8 M

2. Solids Handling

Replace existing thickening equipment that has reached the end of its useful life and is undersized with properly sized, reliable thickening equipment.

Improve the existing digestion process to increase total and reliable capacity to treat current and future loads.

Add new equipment to eliminate the need to haul digested sludge to the Tri-City WRRF for dewatering.

$24.3 M

3. Digester Gas Utilization

Install new gas storage, treatment, and cogeneration systems to increase the beneficial use of fuel produced as a by-product of anaerobic digestion.

$5.9 M

4. R&R Projects Complete near-term, mid-term, and long-term R&R projects as recommended by the condition assessment.

$7.9 M

Total 20-year Investment in the Kellogg Creek WRRF $40.9 M

The proposed site plan for the Kellogg Creek WRRF is shown in Figure 12. This site plan addresses the propriety improvements through the planning period, and retains space for future process improvements to meet more restrictive NPDES permit limits, if needed.

RECOMMENDED PLAN – TRI-CITY WRRF

The planning team also completed a detailed facilities plan for the Tri-City WRRF. Table 9 summarizes projects that are recommended to be completed within the planning period.

Project Description Estimated Capital Cost

1. Peak Flow Hydraulic Improvements

Install a new peak flow treatment process (ballasted sedimentation) south of the existing WRRF to increase peak flow hydraulic capacity to 105 mgd.

NOTE: The ballasted sedimentation process has been used to effectively treat peak wet weather flows at numerous wastewater facilities in Oregon and throughout the US. In the event that this approach does not meet regulatory approval at the Tri-City WRRF, a similar process involving biological treatment may be required. This is expected to cost an additional $30 million; however, the planning team does not believe this additional investment is needed to meet NPDES permit limits and protect Willamette River water quality.

$53.7 M

2. Thickening Improvements

Install new facilities to thicken primary sludge from existing and new primary sedimentation basins.

$7.6 M

3. R&R Projects Complete near-term, mid-term, and long-term R&R projects as recommended by the condition assessment.

$16.9 M

Total 20-year Investment in the Tri-City WRRF $78.2 M

The proposed site plan for the Tri-City WRRF is shown in Figure 13. This site plan includes buildout facilities for space planning purposes and is consistent with the basin-wide recommendation to meet future NPDES limits by expanding the treatment process at Tri-City.

SCHEDULE AND 20-YEAR CIP

Developing a schedule and 20-year CIP for the recommended projects is the final step in the planning process. The schedule must consider numerous factors including the criticality, magnitude, and duration of each project. The availability of funding and overall affordability is also a substantial factor in determining the CIP. For the WFP, the District attempted to “level” the total cash expenditure required in any given year, to mitigate sewer rate impacts through the planning period.

The proposed schedule for the recommended projects at the Kellogg Creek and Tri-City WRRFs is shown in Figure 14. Major projects at each facility include both design and construction phases. R&R projects are distributed uniformly across the time period associated with their priority (i.e., 0 to 2 years, 3 to 5 years, 6 to 10 years). In actuality, these projects may be performed separately through maintenance contracts, grouped together, or included in one of the larger capital projects occurring within the same time period.

The proposed cash expenditure schedule associated with the recommended plan is shown in Figure 15.

The estimated cost of completing each expansion and R&R project is shown for each year of tge planning period. The District’s other investments for projects in the wastewater collection and conveyance system, the Tri-City WRRF Outfall, and/or projects associated with non-process facilities

2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040

Recommended Kellogg Creek WRRF Projects

Disinfection Improvements

Solids Handling Improvements

Digester Gas Utilization Improvements

R&R Projects

Recommended Tri-City WRRF Projects

Peak Flow Hydraulic Improvements

Thickening Improvements

R&R Projects

(e.g., lab and administrative buildings that are needed to support treatment process functions) are not shown in Figure 15.