executive briefing document - public works · the boise system of wastewater management ......

Final Report

City of Boise Wastewater Facilities Plan 2020Part 1 – Executive Briefing Document

Prepared for

City of Boise, Department of Public WorksJune 2010

and

PLANNING FOR A SUSTAINABLE FUTURE.

F i n a l R e p o r t

City of Boise Wastewater Facilities Plan 2020

Part 1—Executive Briefing Document

Prepared for

City of Boise, Department of Public Works

June 2010

Contents

Section Page

Introduction......................................................................................................................................... 5

Sustainability Approach to WWFP Planning................................................................................ 5

Public Participation............................................................................................................................ 7

The Boise System of Wastewater Management............................................................................ 8 Conveyance System ............................................................................................................... 9 Lander Street WWTF ............................................................................................................. 9

Permits and Performance ......................................................................................... 9 West Boise WWTF .................................................................................................................. 9

Permits and Performance ....................................................................................... 10 Twenty Mile South Biosolids Application Site................................................................. 10

Permits and Performance ....................................................................................... 10

What Are the Future Wastewater Management Needs ............................................................. 13 Population, Flows, and Loads Drivers .............................................................................. 13 Regulatory Drivers ............................................................................................................... 22

Phosphorus............................................................................................................... 22 Temperature............................................................................................................. 23

Infrastructure Drivers .......................................................................................................... 24 Conveyance System ................................................................................................ 24 Lander Street WWTF Future Utilization.............................................................. 24 West Boise WWTF Future Utilization .................................................................. 25 Water Reclamation and Effluent Use ................................................................... 25 Growth and Expansion of the Future Service Area to the South and Southeast..................................................................................... 25

Recommended Actions.................................................................................................................... 25 Conveyance ........................................................................................................................... 26

Long-Term Upgrade Projects................................................................................. 26 Lander Street ......................................................................................................................... 31 West Boise.............................................................................................................................. 32

Phosphorus Removal .............................................................................................. 32 Capacity Evaluation ................................................................................................ 35 Additional West Boise WWTF Actions ................................................................ 36

Twenty Mile South Biosolids Application Site................................................................. 36 Future Service Area.............................................................................................................. 39

Implementation and Schedule for the Recommended Actions............................................... 40

Cost Implications.............................................................................................................................. 40

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Tables Page

1 Community Sounding Board Committee Members ..........................................................8 2 Population Projections .........................................................................................................14 3 Near-Term Recommended Sewer Trunk Projects—Opinion of Probable Costs .........26 4 Long-Term Recommended Sewer Trunk Projects—Opinion of Probable Costs .........31 5 TMSBAS Capital Improvement Projects............................................................................39 6 Cost of Near-Term Projects..................................................................................................40

Figures Page

1 Wastewater Services Jurisdictions for Boise Area of Impact ..........................................11 2 Illustration of Boise’s Wastewater Management System ................................................13 3 Lander Street WWTF ............................................................................................................15 4 West Boise WWTF.................................................................................................................17 5 TMSBAS .................................................................................................................................19 6 Flow Projections ....................................................................................................................22 7 Future Service Area Planning Area....................................................................................27 8 Reserve Capacity Area after Downstream Upgrades ......................................................29 9 Decision Chart for Lander Street WWTF Future Utilization ..........................................33 10 West Boise WWTF Site Plan—Total Phosphorus Removal ............................................37 11 Future Service Area Decision Tree .....................................................................................41 12 Five WWTFs FSA Alternative .............................................................................................43 13 Summary of Short-Term Planning and Initial Facilities Planning Actions ..................45

Introduction The City of Boise (City) Department of Public Works began a wastewater facilities planning process to establish an overall systemwide guiding document that prioritizes needs, balances available resources, identifies specific actions, and identifies uncertainties regarding wastewater management and infrastructure.

This facilities plan identifies near-term actions to address immediate needs and provides long-term guidance for future wastewater management needs in the Boise Metropolitan Area. It is anticipated that this plan will be periodically amended as technical and regulatory uncertainties are resolved. Amendments are also sometimes required for obtaining funding from the Idaho Department of Environmental Quality (DEQ).

The facility planning process was formulated along three lines: (1) the development of detailed technical information on which the near-term actions and long-term guidance decisions could be based; (2) a public outreach effort that included the formation of a community sounding board that participated in a series of facilitated review meetings so board members could provide focused input about the detailed technical information; and (3) an alternatives evaluation method applied to multiples of alternatives in a series of six intensive half-day workshops with City staff.

This document is an abbreviated version of the plan that enables the reader to understand the basic strategy rather than focus on the specific details. Detailed supporting information is available in the Wastewater Facilities Plan 2020 document and the Supporting Technical Memorandums.

Sustainability Approach to WWFP Planning Several years ago, the Mayor and City Council developed and adopted a comprehensive Strategic Plan (http://www.cityofboise.org/StrategicPlan/StrategyMap.aspx). This Plan included the following Mission Statement:

We are a dynamic Western city committed to providing exceptional municipal services and partnering to promote a healthy environment and a strong economy, ensuring Boise remains a safe and vibrant community.

The Mission Statement clearly fosters the broad concept of “sustainability,”1 but more pointedly, several key elements of the Strategic Plan focus specifically on both environmental and financial sustainability:

Ensuring a safe, healthy, livable community Being the leader for sustainable development and redevelopment Promoting a strong and diverse local economy Maintaining bond rating and competitive rates and fees

1 Sustainability is defined as the development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Our Common Future, United Nations World Commission on Environment and Development 1987.

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EXECUTIVE BRIEFING DOCUMENT PART 1, BOISE WASTEWATER FACILITIES PLAN 2020

At the very beginning of the facilities planning project, three workshops were conducted to ensure that the wastewater plan would be in alignment with the Strategic Plan, and to establish a methodology for evaluating wastewater plan alternatives consistent with the Strategic Plan. For example, one of the key evaluation criteria was environmental impact (see Recommended Actions section for the other criteria). This criterion compared alternatives by determining how well each provides better effluent quality than required by permit or other beneficial environmental impacts. Does the system utilize alternative energy, improve air quality, reuse or conserve water? Consistent with the Mayors’ agreement, one of the key environmental impact metrics was associated with the greenhouse gas (GHG) emissions, or carbon footprint, of each alternative. Therefore, the GHG emissions from and energy used at the treatment facilities were quantitatively determined for each major alternative.

Thus, consistent with the City’s Strategic Plan, a sustainable wastewater facilities plan encompasses environmental, fiscal, and social considerations. And in fact, these sustainability concepts are already applicable to existing wastewater operations. For example, biosolids generated as a byproduct at the City’s wastewater plants are applied to farmland at the City’s Twenty Mile South Biosolids Application Site (TMSBAS), thereby providing a natural source of fertilizer for the crops, which are in turn sold to local dairies for animal feed, bringing a revenue stream back to the City. This is an example of both environmental and financial sustainability. Another example is the WaterShed facility that the City opened in May 2008, which is an educational and administrative facility with meeting room, theater, and exhibits on water, wastewater and environmental sustainability.

A critical aspect of ongoing financial sustainability is the City’s policy that growth pays its own way, specifically for wastewater facilities as noted below:

New capacity is paid by new users through connection fees Repair and replacement of existing facilities is funded by monthly service charges Upgrades resulting from regulatory requirements are funded by existing customers and

new users

The City also recognized that wastewater planning must be informed by, and integrated with, the broader water resources planning processes within the Treasure Valley. For example, the geographical planning boundary for wastewater management in the Future Service Area to the south and southeast (FSA) must take into account the potential availability of water to serve this growth area. Also, the amount of wastewater that could be reused in this same area will have a major influence on how much other water will actually be needed there. As a result, this wastewater facilities plan also evaluated a “Total Water Management” (TWM) approach as part of development of the City’s long-term water strategy. A TWM approach is the key to development of a sustainable water supply for the region’s future. TWM is an approach that integrates relevant aspects of the water cycle to sustainably manage our water resources. This approach is particularly important in the context of increasing water scarcity, competing demands, environmental preservation, and public expectations.

As part of this TWM effort, the Boise City Council appointed a Water Resource Advisory Committee (WRAC) to assist with the implementation of an initiative identified in Boise’s Strategic Plan. The initiative called for the City to complete a comprehensive strategic water plan that makes adequate provision for growth while protecting our most important natural

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PART 1, BOISE WASTEWATER FACILITIES PLAN 2020 EXECUTIVE BRIEFING DOCUMENT

resources. The WRAC worked through a series of workshops to define more specific goals and objectives that a comprehensive water policy should serve; identify and evaluate a number of “management models” that may be used to effect water policy implementation; and delineate a number of near-term recommendations for City Council action.

One of the key outcomes of the TWM evaluation process was the recognition of the future importance of wastewater reuse as a key element of the City’s long-term water strategy. It represents a valuable source of future water that provides the City with some opportunity in water management. It also helps with discharge permit requirements. Reusing wastewater provides the City consistency with its Strategic Plan, and provides leverage in water management, both with other domestic water providers and with irrigators.

Because of the importance of sustainability, it served as the underlying theme of the project:

As described below in the Executive Briefing Document, elements of sustainability thread throughout the analyses and recommended actions, including the following examples:

Choosing the use of natural biological processes to remove phosphorus (as opposed to chemicals), and recovery of the removed phosphorus for use as fertilizer (good for environmental sustainability and provides a commodity revenue stream for the city)

Selecting a treatment alternative with low GHG emissions. The selected natural biological process alternative for the West Boise WWTF generates 21 percent less GHG emissions when compared to chemical treatment.

Implementing a combined heat and power facility that converts digester gas into electricity and recovers waste heat to supplement process and building heating requirements. This action converts waste digester gas into a renewable energy resource that offsets WWTF needs.

Implementing waste receiving facilities to increase digester gas production. This action recycles waste material such as grease trap pumpage into a renewable energy resource to further offset WWTF needs.

Recommending that the buildout model in the FSA to the south and southeast of the City is to reuse wastewater for turf irrigation (landscapes, golf courses, open spaces, roadsides, and greenbelts). The biosolids would be applied to agricultural land at the TMSBAS.

Public Participation A Boise Wastewater Facility Plan 2020 Community Sounding Board was formed to obtain a more in depth public perspective on the future of wastewater management for the City. Volunteers from environmental organizations, citizen groups, businesses and concerned

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business groups, and government agencies participated as the primary stakeholders in the CSB. Table 1 lists the individuals who served on the Community Sounding Board Committee.

TABLE 1 Community Sounding Board Committee Members

Member Affiliation

Bekah Cooper Veterans Park Neighborhood

Doug Fowler Lenir Ltd.

Justin Hayes Idaho Conservation League

Charles Hummel Idaho Smart Growth

Kevin Lewis and Liz Paul Idaho Rivers United

Lisa Luna Micron

Mark Mason Idaho Department of Environmental Quality

Brian McDevitt Southeast Neighborhood Association

Renee Quick Resident and Public Works Commission

Scott Rhead United Water Idaho

Ray Stark Boise Metro Chamber of Commerce

Tom Turco Resident

Barry Teppola The Legend Company

Four initial CSB meetings were facilitated which discussed the following topics: (1) purpose of CSB, (2) existing facilities, (3) Facilities Plan issues and drivers, and (4) descriptions of alternatives. CSB Meeting 5 was held to describe the non-monetary and monetary evaluation of the wastewater management alternatives. Meeting 6 focused on getting input from CSB members on how to best present Facilities Plan information to the public in an open house format. The CSB then participated in the open house/public hearing, which was held on September 22, 2009.

The Boise System of Wastewater Management To understand the current system of wastewater management, it is important to understand its history. The first sewers in the Boise valley were installed during the 1890s, and from then until 1950 untreated wastewater was discharged directly to the Boise River. In 1950 the City’s first wastewater treatment facility (WWTF), the Lander Street WWTF, was commissioned. The Bench Sewer District, the Northwest Boise Sewer District, and the West Boise Sewer District were formed to provide wastewater conveyance services in the expanding areas of Boise. The West Boise WWTF was commissioned in 1976. Also at that time, the Garden City WWTF was abandoned, and their wastewater was conveyed to the West Boise WWTF for treatment. In 1992 sewers were extended into the southwest community at the request of the Ada County Board of County Commissioners. In the mid 1990s 2,400 acres were purchased for managing biosolids from the WWTFs, and another 1,900 acres have been added since then for future use. In 1997 the Eagle Sewer District connected to the City system. Today sufficient capacity is available to carry the City well

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into the next decade. However, changes in treatment will be required in the near future to remove phosphorus. Current practices consistently exceed permit standards and other regulatory requirements.

Figure 1 shows the wastewater system service jurisdictions for Boise’s Area of Impact. Figure 2 schematically illustrates the features of the City of Boise’s wastewater conveyance and treatment system.

Conveyance System The City’s wastewater conveyance system consists of gravity sewer pipes, pressure pipes/siphons, and pump stations which convey wastewater to the City’s two WWTFs. The City’s system includes 682 miles of gravity sewer pipe ranging from 6 to 72 inches in diameter. Of this amount, about 14 miles are considered to be in substandard or poor condition and in need of attention or corrective action to maintain a high level of service. The City also operates and maintains five major pump stations.

Lander Street WWTF The Lander Street WWTF has been expanded numerous times for capacity and efficiency. It is currently rated at 15 million gallons per day (mgd) and provides advanced secondary treatment with ammonia removal. All of the treated wastewater from the Lander Street WWTF is discharged through a submerged diffuser to the Boise River. The Lander Street WWTF also provides treatment of residual solids. The solids are pumped to the West Boise WWTF for dewatering. The Lander Street WWTF and the adjacent neighborhood are shown in Figure 3.

Permits and Performance The Lander Street WWTF is permitted to operate under a federally issued National Pollutant Discharge Elimination System (NPDES) permit. The permit contains effluent limitations for pH, 5-day biochemical oxygen demand, total suspended solids, and fecal coliform bacteria. There currently is no effluent limitation for phosphorus.

Effluent quality from the Lander Street WWTF meets or exceeds the requirements contained in the NPDES permit. No enforcement actions or fines have been brought against the City for violations of the Clean Water Act from operation of the Lander Street WWTF. The Lander Street WWTF was honored in 2007 by receiving a Gold Peak Performance award from the National Association of Clean Water Agencies. The Gold award honors treatment works that have achieved 100 percent compliance with their NPDES permit for an entire calendar year.

West Boise WWTF The West Boise WWTF currently has an NPDES design flow of 24 mgd. The City has recently completed a capacity optimization study for this WWTF. The outcome and implementation plan for additional capacity are discussed later in this document. The WWTF secondary treatment processes are arranged into a North Plant and a South Plant configuration and provide advanced secondary treatment with ammonia removal. All treated wastewater is discharged to the south channel of the Boise River. The West Boise WWTF also provides treatment of residual solids. The processed residual solids (biosolids)

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from the West Boise WWTF and the Lander Street WWTF are combined and dewatered at the West Boise WWTF. The West Boise WWTF and the adjacent areas are shown in Figure 4.

Permits and Performance The West Boise WWTF is permitted to operate under a federally issued NPDES permit. The permit contains effluent limitations for pH, dissolved oxygen, 5-day biochemical oxygen demand, total suspended solids, lead, and fecal coliform bacteria. Currently, there is no effluent limitation for phosphorus.

There have been no enforcement actions or fines brought against the City for violations of the Clean Water Act from operation of the West Boise WWTF. The West Boise WWTF was honored in 2007 by receiving a Platinum 6 Peak Performance award from the National Association of Clean Water Agencies. The Platinum 6 award recognizes 100 percent compliance with the NPDES permit over a consecutive 6-year period.

Twenty Mile South Biosolids Application Site The City owns and operates a farm called the Twenty Mile South Biosolids Application Site (TMSBAS). The dewatered biosolids are trucked from the West Boise WWTF to the TMSBAS and applied to the fields to improve the soil and benefit agricultural production. Figure 5 shows an aerial view of the TMSBAS.

Permits and Performance The TMSBAS is also permitted to operate under a federally issued NPDES permit. Eight pollutants of concern are regulated (arsenic, cadmium, copper, lead, mercury, nickel, selenium, and zinc). Pollutant concentrations for biosolids that are applied to agricultural lands cannot exceed applicable ceiling or monthly average pollutant concentration limits, and cumulative loading rates. The City has consistently produced Class B biosolids below pollutant ceiling concentrations for the past 15 years. In addition, the permit regulates nutrient application through agronomic rate management.

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EAGLE

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PLANNING FOR A SUSTAINABLE FUTURE.PLANNING FOR A SUSTAINABLE FUTURE.WB122008001BOI

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FIGURE 1

WASTEWATER SERVICES JURISDICTIONS FOR BOISE AREA OF IMPACT


FIGURE 2 Illustration of Boise’s Wastewater Management System

What Are the Future Wastewater Management Needs The City’s future needs arise from:

Responding to the demands for wastewater service that arise from unpredictable cyclic growth that may occur within or near the current area of impact.

Responding to current and future regulatory mandates for control of phosphorus, potentially temperature, and micro-constituents also referred to as endocrine disrupting compounds, and pharmaceuticals and personal care products.

Providing competitive and cost efficient wastewater services while investing in facilities that remain long-term assets.

These wastewater management needs are discussed below.

Population, Flows, and Loads Drivers Historical population was reviewed to determine recent growth rates to aid in estimating the time period when the buildout population may occur within the current area of impact. Based on the 1991 to 2007 data, the City population increased 54 percent and the average annual growth rates ranged from zero to 9 percent. The higher annual growth rates (9 percent) are likely due to annexations.

Table 2 summarizes several population projection scenarios. The buildout population (the anticipated population expected to occur in the current area of impact when it is fully

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developed) is an important planning consideration and is estimated to be 387,661 for Boise and Garden City. By comparison the buildout of the FSA to the south and southeast of the City (FSA) is estimated to be 429,000.

For example the buildout population in the current area of impact would occur around 2026 if the City’s population grows at an average of 3.0 percent each year. If the City’s population grows at an average of 2.0 percent each year full buildout takes another 10 years or in 2036 (see Table 2). At 1.0 percent each year the buildout population would not occur until about 2064. So the rate of growth over the long term is a major factor in facilities planning.

During the 10 years from 1998 to 2007, the estimated population for Boise, Garden City, and Eagle increased from 207,496 to 233,648, or about 12.6 percent. This equates to an annual growth rate of 1.33 percent over the same period. During that period, Boise and Garden City populations grew at about 1 percent per year, while Eagle grew at more than 6 percent per year.

TABLE 2 Population Projections

Average Annual Growth Rate and Population Projection

Year Existing Population 1.0 2.0 3.0

2007 222,086

2010 228,815 235,679 242,679

2015 240,487 260,209 281,332

2020 252,755 287,292 326,141

2025 265,648 317,193 378,087

2030 279,198 350,207 438,306

2035 293,440 386,657 508,117

2040 308,409 426,901 589,047

NOTE: Bolded values exceed the estimated buildout population for the current areas of impact for Boise and Garden City.

Despite the modest growth each year in population the annual average daily flow to the WWTFs has not tracked with population and was relatively flat during this same period. Per capita contributions ranged from 112 to 128 gallons per capita per day with 118 being the average for the period. Average flow to the WWTFs was 26.36 mgd.

A significant factor is the average daily flow that occurs during the peak month. This flow value correlates with the permitted values for the WWTFs. A sampling of average day peak months flows is as follows:

1995 = 23.5 mgd 2000 = 29.5 mgd 2005 = 28.4 mgd 2006 = 30.1 mgd 2007 = 27.8 mgd

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WB122008001BOI PLANNING FOR A SUSTAINABLE FUTURE.PLANNING FOR A SUSTAINABLE FUTURE.

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Other factors, in addition to service population and growth, impact the amount of flow that arrives for treatment at the WWTFs. This is because growth in flow does not always mirror growth in population and must be accounted for in the planning and design of facilities. Figure 6 shows what happens when flow growth is increased by 1, 1.5, and 2 percent per year. The 2 percent per year flow growth rate exceeds the current capacity of the WWTFs before 2030. The 1.5 percent flow growth rate equals the capacity of the WWTFs around 2029, and the 1 percent per year growth rate means capacity would remain in the WWTFs by 2030. Within the current area of impact, there is reserve treatment capacity of about 8 or 9 mgd in the system. If the next 10 years of population and flow growth are similar to the last 10 years, then population and flow growth are not significant drivers in the current area of impact. However, in the FSA no treatment capacity is available, and population growth in that area would be a significant driver.

The most important factors beyond population growth include:

Industrial contributions to flows and loads can be highly variable and unpredictable. For example, even a single large industrial user, either a new one coming into the system or an existing one making substantial increases or decreases, can have major effects.

Ongoing and future water conservation efforts are likely to reduce flows. The City’s per capita wastewater flows have been going down historically, and may be expected to drop even further as conservation programs evolve—in particular as GHG reduction initiatives influence the activities of water providers. Another potential future conservation concept involves reuse of gray water. While not prevalent today in Idaho,2 it could become more common in the future, especially in newly developing areas.

The City has had a robust program underway to repair and rehabilitate old and leaky sewers that would otherwise allow rainwater to inflow and groundwater to infiltrate into the system. Reduction in this “I/I” offsets increased flows from other sources and extends system capacity and treatment efficiency.

2 This facilities plan evaluated the concept of gray water reuse as summarized in a separate Technical Memorandum. In the U.S., gray water generally is defined as domestic wastewater from residential clothes washers, bathtubs, showers and sinks, but not including wastewater from kitchen sinks, dishwashers and toilets. Idaho further excludes water softener wastewater. Gray water use is normally restricted to subsurface outdoor irrigation and is subject to applicable state and local regulations and plumbing codes.

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FIGURE 6 Flow Projections

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Regulatory Drivers Total Maximum Daily Load (TMDL) is a specific limit on pollutants in wastewater and from other sources that can be put into a stream, river or lake so that the water quality goals of the water body can be achieved. Current TMDLs that pertain to the Lower Boise River include five pollutants of concern for the City’s WWTFs: sediment, bacteria, phosphorus, mercury, and temperature. The U.S. Environmental Protection Agency (EPA) approved the TMDL for sediment and bacteria in January 2000. No significant adverse implications are expected for the City regarding sediment, bacteria, or mercury.

Phosphorus Phosphorus is a naturally occurring element, and is an essential nutrient for a healthy aquatic ecosystem. When present in elevated concentrations, however, it can cause excessive aquatic plant and algae growth. Such excessive growth can cause nuisance conditions and a diminished aesthetic quality for the affected lake, river, or stream. In addition, this plant and algal matter eventually decays, and in the process consumes some of the dissolved oxygen in the water that is necessary for other aquatic life like insects and fish. These kinds of impairment currently exist in the Snake River which led to the need for the Snake River-Hells Canyon (SR-HC) TMDL for phosphorus. Because the problems associated with phosphorus are most prevalent during the growing season, the SR-HC TMDL established May through September as the seasonal period when phosphorus reductions are needed.

The SR-HC TMDL was developed jointly by the Oregon and Idaho Departments of Environmental Quality, and was approved by the EPA in 2004. This TMDL established

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phosphorus targets not only for the Snake River, but also to major tributary rivers like the Boise River. In 2008, the DEQ, in cooperation with the Lower Boise Watershed Council, developed a formal plan to implement the SR-HC TMDL for the lower Boise (Lower Boise Watershed Council and DEQ, 2008). This implementation plan established phosphorus reduction goals for all sources in the watershed, including the City’s WWTFs. The City’s reductions will be mandated via the federal NPDES permits that are issued by the EPA. What the final permit limits will be is uncertain at this point, but could range from 0.07 milligram per liter (mg/L or part per million), which is the SR-HC target, to 0.2 mg/L (the implementation plan requirement for WWTFs). To put this in perspective, the current levels of phosphorus in the City’s treated effluents range from about 4 to 6 mg/L, which means that the City will have to achieve a reduction of greater than 95 percent.

For WWTFs, these new limits will require the upgrading of existing treatment systems or, in many cases, construction of new treatment plants to provide some form of biological nutrient removal (BNR). At the present time, the most widely used form of BNR involves use of suspended growth (activated sludge) treatment systems. These systems provide the biological steps necessary to remove nutrients like phosphorus from the wastewater. BNR alone, however, cannot reduce phosphorus all the way to the target levels cited above (BNR alone can generally get to about 1.0 mg/L); therefore some additional treatment via chemical addition and filtration will be needed.

It is also critical to the Boise City long-term wastewater facilities planning to understand that the phosphorus implementation plan adopted by the DEQ anticipates that 50 percent wastewater reuse will be accomplished for new municipal growth and development that occurs beyond a 15-year horizon. A lumped reserve for growth has been developed to accommodate future WWTF needs anywhere in the watershed. The reserve for growth assumes that between year 15+ and final TMDL attainment, WWTF reuse will increase to an ultimate level of 50 percent for sources that come online during that time.3 This expectation for future reuse has significant implications for growth and development in the FSA south and southeast of the City.

The current NPDES permits expired in November 2004, but have been administratively extended because the City submitted timely and complete permit renewal applications. Renewed draft permits are anticipated to be issued sometime in 2010, and effluent limitations for phosphorus are anticipated to be in those reissued permits, along with a schedule of compliance to achieve the limits.

Temperature The lower Boise River from Star to the Snake River has been listed as impaired by high temperature since 1996. This is because existing water temperatures exceed the criteria applicable to the river at certain locations during certain times of the year. Some fish species in the river, such as trout, prefer colder water and that is why temperature is an issue. The DEQ determined in the lower Boise TMDL (DEQ, 1999) that point source discharges and agricultural return flows are not significant thermal sources, and that climate and elevation preclude attainment of the main stem temperature criteria. The DEQ suggested delisting the 3 Note that the 50% reuse goal is linked to the implementation plan limit for WWTFs of 0.2 mg/L. If WWTFs remove phosphorus to 0.07 mg/L, either by choice or if required by the EPA, then those WWTFs can meet their overall TMDL goal and the reserve for growth can be accommodated without the reuse component of the plan.

BOI091560001.DOC/WBG050310052451BOI 23


river for temperature impairment and also suggested alternative regulatory approaches to address temperature conditions. In fact, the river was not delisted for temperature in subsequent listings, and in 2000 the river from Star to Diversion Dam was added by the EPA. In 2000, the EPA also approved the lower Boise River sediment and bacteria TMDLs, and took no action regarding the temperature discussion contained in the 1999 TMDL document.

The SR-HC temperature TMDL identified natural conditions in the main stem Snake River as being potentially responsible for observed temperatures greater than the criteria. Nonetheless, the TMDL requires a temperature assessment for each of the five major tributaries, including the lower Boise River, to determine if temperature increases in these tributaries are due to anthropogenic (human-caused) or natural causes. If anthropogenic sources are determined to cause more than the allowable increase, a follow-up temperature TMDL is required.

No further regulatory action has been taken to date by the DEQ or the EPA related to temperature in the lower Boise River. The Boise River temperature issues are still currently awaiting a regulatory solution. Like phosphorus, it is anticipated that regulation of temperature will have a seasonal basis. The river is warmest in July and August, of course, and so the summer season would be a critical one. In addition, temperature criteria are established to protect fish spawning activities. Rainbow trout spawn in spring, for example, and thus this season could also be included in the evaluation.

The issue regarding future effluent temperature requirements is potentially critical to the City of Boise wastewater facilities planning. River modeling work done by the City shows that most of the thermal load from the Lander Street WWTF in the summer will have dissipated before reaching the West Boise WWTF. The future West Boise thermal load, even with Lander Street retained, would be substantial enough that some form of offset or mitigation might be needed assuming temperature TMDLs and implementation plans follow the precedents in Oregon versus applying chilling or cooling technologies at the WWTFs. Thus, transferring all of the thermal load to the West Boise WWTF via decommissioning Lander Street WWTF would not be taking full advantage of the assimilative capacity of the river.

The temperature TMDL has not been established to date. Effluent limitations for temperature are not anticipated if the renewed draft permits are issued sometime in 2010.

Infrastructure Drivers

Conveyance System The capability of the existing conveyance system to accommodate buildout of the City’s area of impact is a major driver in this planning study. The extent to which the conveyance system can be leveraged to serve growth in the FSA is also important. Perhaps bottlenecks should be removed to optimize its overall capacity and performance.

Lander Street WWTF Future Utilization The issue of whether the Lander Street WWTF has served its useful purpose and should be retired is another major driver in this planning study. The issue is made more important as

24 BOI091560001.DOC/WBG050310052451BOI


the City faces an investment to satisfy effluent limitations for phosphorus in the near future. Therefore, does it make sense to: (1) invest in the facility strictly for phosphorus compliance; (2) invest in the facility more substantially to replace aging equipment and process units, and for phosphorus compliance; (3) replace the facility completely with a modern facility capable of phosphorus compliance; or (4) abandon the facility and invest in the West Boise WWTF for phosphorus compliance?

West Boise WWTF Future Utilization The West Boise WWTF is considered to be the significant WWTF in the Boise system for the long term. This larger and newer facility is located at the downstream end of the area of impact. The West Boise WWTF is surrounded by City-owned land that may provide additional space for treatment and buffers to accommodate buildout populations. Clearly it is a logical choice for centralized treatment and discharge. So a future decision is whether to expand and accommodate treatment for the flows being treated at the Lander Street WWTF.

Water Reclamation and Effluent Use The issue of whether reuse of treated wastewater has a role in solving the future wastewater management needs is another important question. Perhaps reuse will play a part to offset the cost of compliance for phosphorus reductions at the Lander Street WWTF, the West Boise WWTF, and for the FSA. Opportunities for reuse in the built environment are limited.

Growth and Expansion of the Future Service Area to the South and Southeast The potential for growth is strongest to the south/southeast of the City creating the likelihood of a future expansion of the City’s area of impact. The planning area in the FSA contains approximately 42,900 acres (see Figure 7). Assessing the “big picture” infrastructure alternatives that satisfy that area’s needs for the conveyance, treatment, discharge, and reuse of wastewater is a major driver.

Recommended Actions Hundreds of combinations of wastewater conveyance and treatment alternatives were developed and evaluated based on non-monetary and monetary criteria.

The following non-monetary evaluation criteria were developed by City staff and the consultant team. These criteria were developed based on the objectives of the Strategic Plan and were used to compare alternatives:

System reliability Adaptability/phasing/flexibility Operability Social impacts Environmental impacts

Monetary comparisons for alternatives were made using the net present value method. Net present value uses the time value of money to equate capital costs, operation and maintenance costs, and salvage values to an equivalent present day total. Capital costs included costs for construction, engineering, land acquisition, easements, project

BOI091560001.DOC/WBG050310052451BOI 25


administration, and contingency. Operating costs include annual expenses related to new infrastructure or those resulting from potential changes to operating procedures. All capital and operating forecasts are shown in 2008 dollars.

Conveyance Using computer modeling of the entire conveyance system, projects to upgrade the conveyance system were identified to accommodate the treatment alternatives for buildout.

The near-term upgrade projects are limited to the Warm Springs Trunk where upsizing the Harris Ranch Lift Station and force main is recommended. A second near-term conveyance project is pre-design of the diversion facilities for flow in and out of the Lander Street WWTF to the South Boise Interceptor for operational flexibility. Finally, ongoing sewer rehabilitation is recommended to reduce infiltration and inflow and replace defective pipe at $800,000 per year. Opinion of probable construction costs for the Lander Street diversion will be developed during the pre-design phase. Table 3 shows the near-term recommended sewer trunk projects and their probable costs. Figure 8 shows the approximate location of these projects.

TABLE 3 Near-Term Recommended Sewer Trunk Projects—Opinion of Probable Costs

Service Area

Opinion of Probable

Construction Cost

Warm Springs Trunk

Upsize Harris Ranch Lift Station to ultimate pumps and interior piping. Install ultimate force main to discharge at Warm Springs Golf Course

$1,700,000

Lander Street WWTF Interceptor and Diversion

Lander Street Interceptor Repair or Replacement and Diversion for flow in/out of the Lander WWTF to the SBI

$3,000,000

Systemwide Sewer Rehabilitation to reduce infiltration and inflow and rep[ace defective pipe @ $800,000 per year for 5 years

$4,000,000

Total (2008 dollars) $8,700,000

Long-Term Upgrade Projects Long-term projects install downstream upgrades of the existing sewer trunk to provide sewer service to the City Impact Area. Table 4 shows the long term recommended sewer trunk projects and their probable costs.

26 BOI091560001.DOC/WBG050310052451BOI


North

0 421 3

Approximate scale in miles

FIGURE 7

FUTURE SERVICE AREA PLANNING BOUNDARY

EAGLE

Kuna Mora Rd.


Kuna Planning Boundary

!10-1

! 8-1

! 5-1

!5-2

!

SE-2

!WS-1

!SE-1

Boise

Eagle

Meridian

Garden City

3N2E

2N2E2N1E

3N1E

4N2E4N1E

2N3E

3N3E

4N3E

1N1E 1N2E 1N3E

5N1E 5N2E

4N1W

3N1W

2N1W

1N1W

5N1W Legend

Final Available Service After Upgrades

Initial Available Service


Current Area Served

S/SE Future Sewer Planning Area


Sewer Trunks

18 - 21"

21 - 27"

27 - 36"

36 - 48"

48 - 72"

0 12,500 25,0006,250

4


North


FIGURE 8

RESERVE CAPACITY AREA AFTER DOWNSTREAM UPGRADES


TABLE 4 Long-Term Recommended Sewer Trunk Projects—Opinion of Probable Costs

Service Area Opinion of ProbableConstruction Cost

5-1: 1,370 linear feet of 18-inch parallel trunk from Manhole (MH) SW4113 to MH SW4106

$600,000 Five Mile Trunk

5-2: 1,150 linear feet of 18-inch parallel trunk from MH SW4033 to MH SW4028

$500,000

Eight Mile Trunk 8-1: 3,650 linear feet of 24-inch parallel trunk from MH SW 30166PL to MH SW30150

$1,400,000

Ten Mile Trunk 10-1: 3,650 linear feet of 24-inch parallel trunk from MH SW275 to MH SW277

$300,000

Southeast Trunk SE-1: 1,400 linear feet of 18/24-inch parallel trunk from MH 562B16 to MH 56212. Modify MH 562B12 to a Diversion Structure

$800,000

Five Mile Trunk 5-3: 355 linear feet of 18-inch parallel trunk from MH SW4140 to MH SW4138

$200,000


$2,200,000


$1,100,000


$600,000


$800,000

Eight Mile Trunk


$600,000

Southeast Trunk SE-2: Remove existing 33-inch pipe and install a new 48-inch trunk from MH 254 to the Americana Diversion

$2,200,000

Total (2008 dollars) $11,300,000

NOTE: Value Engineering was not completed to determine the best upgrade option(s). Value Engineering will need to be completed in future planning efforts to optimize routing and determine cost-effective solutions.

Lander Street The development and initial screening of numerous alternatives for the future use of the Lander Street WWTF resulted in two alternatives that merit future evaluation.

One alternative calls for decommissioning the Lander Street WWTF. The wastewater normally treated at the Lander Street WWTF would be directed through the South Boise Interceptor to the West Boise WWTF for treatment.

The second alternative calls for retaining the Lander Street WWTF to provide liquids-only treatment for 15 mgd. The alternative also calls for substantial replacement of many of the existing liquid treatment processes. These process replacements include new influent screening and flow measurement, new combined primary clarification and grit removal

BOI091560001.DOC/WBG050310052451BOI 31


with degritted primary sludge pump station, one new secondary clarifier with new return activated sludge pumps, and new ultraviolet disinfection. The existing solids treatment facilities would be abandoned and demolished. Treatment upgrades that are capable of producing effluent total phosphorus concentrations of 0.2 mg/L would also be added. These upgrades include conversion of the existing activated sludge basins to provide enhanced biological phosphorus removal (EBPR), a new secondary effluent pump station, and a new secondary effluent filtration facility with chemical storage and dispensing capabilities. With this alternative, degritted primary solids would be conveyed through the South Boise Interceptor to the West Boise WWTF, and the unthickened waste activated solids would be conveyed to the West Boise WWTF through the sludge pipeline. The estimated capital cost of this alternative is $52,100,000.

The decision to decommission or retain the Lander Street WWTF is not necessary at this time in the absence of knowing future NPDES permit requirements for phosphorus, temperature, and sludge conveyance in the South Boise interceptor.

Only constructing facilities that will be needed in any future case is the strategy for the near term for the Lander Street WWTF. This action minimizes capital expenditures and eliminates replacement of facilities that will not be needed for the long term. If maintained for the long term, however, the Lander Street WWTF should be substantially rebuilt and upgraded to meet future effluent limitations for phosphorus.

So the recommended action for the Lander Street WWTF over the next 5 years is:

Maintain the WWTF operation without significant capital improvements. Only construct facilities that will be needed in any future case.

The decision to decommission or rebuild the Lander Street WWTF will be determined in the future. A simplified roadmap for making this decision in the future is presented in Figure 9.

West Boise

Phosphorus Removal Hundreds of combinations of alternatives for the West Boise WWTF were evaluated during the planning study. The alternatives were compared using the non-monetary and monetary criteria previously cited. This process led to the selection of a total phosphorus removal alternative that captures phosphorus for use as a beneficial resource, optimizes the existing capacity of the WWTF, and promotes operational efficiency.

The following components planned for incorporation into the West Boise WWTF:

Two North Plant aeration basins converted to the Johannesburg process Phosphate release tank Primary sludge fermentation system Waste Activated Sludge thickening facilities expansion Struvite precipitation/crystallization system Chemical addition for backup and trimming

The recommended action for the West Boise WWTF is to construct EBPR to remove phosphorus to less than 1.0 mg/L. The estimated cost for this action is $20,900,000.

32 BOI091560001.DOC/WBG050310052451BOI

Facilities ActionsContingent onLander Street

Decision

DecommissionLander St WWTF

Option

KeepLander St WWTF

Option

Temporarily operate LS at minimum flow

load to reduce construction issues & to minimize chemical phosphorus removal

Construct LS replacement process units: screening, UV, PCs, AB mods,sludge

pipeline to WB, demolition

Construct WB plant effluent discharge

facilities, if discharge is changed.

Construct WB plant additional required

phosphorus removal facilities

Construct LS plant additional required


Maximize WB plant capacity without

addition of aeration basins & clarifiers

Construct WB plant effluent discharge

facilities

Construct WB facilities to increase

firm capacity as needed to treat total

system load

Decommission LS and convert to

alternative usage

Construct WB plant additional required


Do we keep LSas WWTF siteand permitted

discharge?

Only WB effluent option is river discharge &

temperature is an unresolved

problem

Desire forreuse plant Desire for

reuse plantDesire for

reuse plant

Unresolved discomfort with loss of permitted discharge

point

Yes if:

or or


FIGURE 9

DECISION CHART FOR LANDER STREET WWTF FUTURE UTILIZATION


While future limits are expected to be more stringent, the recommended action will take the initial step in meeting future final limits. Additional treatment processes are planned to reduce the effluent phosphorus level to either 0.2 mg/L or 0.07 mg/L.

Capacity Evaluation The City also performed a treatment process optimization study for the West Boise WWTF. This study was accomplished in conjunction with the City’s project to modify the West Boise WWTF to meet anticipated future effluent phosphorus limitations. The City wanted to explore opportunities to increase the treatment plant capacity in conjunction with the phosphorus removal project. The optimization study was submitted to the DEQ for review and approval. The DEQ subsequently provided an approval letter to the City, dated January 28, 2010.

The optimization study identified some limitations that reduce the capacity and reliability of the facility. These limitations will be eliminated with two ongoing capital improvement projects: (1) the West Boise phosphorus removal project and (2) the West Boise UV disinfection project. These projects are referenced as Phase 1 and are meant to maintain the 24-mgd capacity rating while incorporating additional reliability and providing effluent phosphorus from 0.6 to 1.0 mg/L, as described previously. Phase 1 actions also include waste activated sludge thickening capacity integrated as part of the phosphorus removal project, South Plant secondary clarifier replacements, and adding a third UV disinfection channel and new UV disinfection equipment.

In order to not preclude taking the Lander Street WWTF offline during the next NPDES permit cycle, the City also identified actions needed at the West Boise WWTF to increase its capacity to 32 mgd. These actions are referenced as Phase 2 and would be implemented if it is decided to decommission the Lander Street WWTF. Some of the Phase 2 actions may be implemented to increase treatment process flexibility and reduce risk of permit compliance or to increase the overall system capacity. Phase 2 actions include the following: (1) adding a process aeration blower, primary clarifier, influent pump, and anaerobic digester; (2) modifying two North Plant secondary clarifier mechanisms; and (3) replacing influent screening equipment.

A third phase of improvements has also been identified that would increase the rated capacity of the West Boise WWTF from 32 mgd to 39 mgd. Phase 3 actions would be implemented if the Lander Street WWTF was taken offline and the overall systemwide capacity needed to be increased to accommodate flow growth. Phase 3 actions include adding another gravity thickener, bioreactor, and secondary clarifier. The City needs flexibility so the next NPDES permit does not restrict how much flow can be treated and discharged from the West Boise WWTF. This is important when considering the City’s NPDES permits are typically administratively extended beyond the normal permit cycle before being reissued.

The phosphorus removal upgrades noted previously would be commensurate with the 32- and 39-mgd capacities for Phases 2 and 3, respectively.

BOI091560001.DOC/WBG050310052451BOI 35


Additional West Boise WWTF Actions Additional West Boise WWTF recommended actions include the following:

Implement a combined heat and power facility that converts digester gas into electricity and recovers waste heat to supplement process and building heating requirements. The action consists of a single-engine generator sized at approximately 1-megawatt capacity to operate on biogas (digester gas) from municipal wastewater, on natural gas, or on a blend of the two gases. The action will connect the generator to the Idaho Power Company system, the existing WWTF electrical system, and will automatically transfer between the two uses. This action converts waste digester gas into a renewable energy resource that offsets WWTF needs. The estimated cost for this project is $3,500,000.

Implement a waste receiving facility to increase digester gas production. This action recycles waste material into a renewable energy resource to further offset WWTF needs. The estimated cost for this project is $400,000.

Optimize capacity by removing hydraulic bottlenecks around the North and South Plant primary clarifiers. Modify the flow split from the headworks to the primary clarifiers to further optimize the hydraulic capacity in the system. Connect the primary effluent piping between the North and South Plants to improve the overall redundancy in the primary treatment system. Theses actions will expand the capacity of the WWTF to achieve optimum performance of all treatment process units. The estimated cost for this project is $5,300,000.

Optimize the reliability and performance of the existing UV disinfection system. A separate study is ongoing to determine the appropriate improvements available within the existing UV disinfection system. The estimated cost for this project is $4,000,000.

Pilot test effluent filtration technologies and chemical addition when the initial phosphorus reduction project is operational. This action will demonstrate the performance of the proposed facilities and serve as the basis for selecting the optimum follow-on technologies to achieve lower effluent phosphorus concentrations in the future.

Optimize WWTF operation for sludge settleability, nitrification, and EBPR. This action will ensure optimum performance of the modified WWTF and extend its capacity.

The West Boise WWTF site plan showing the locations of these actions is presented in Figure 10.

Twenty Mile South Biosolids Application Site Biosolids generated from the City’s WWTFs should continue to be applied at the Twenty Mile South Biosolids Application Site (TMSBAS) to support agriculture for the long term. Near-term actions include proceeding with capital improvements to sustain farm operations. The TMSBAS improvements are related to maintaining the farm equipment and appurtenances for continued operation. Table 5 summarizes the recommended improvements for the TMSBAS.

36 BOI091560001.DOC/WBG050310052451BOI

0 300200100


North

FIGURE 10

WEST BOISE WWTF SITE PLAN–TOTAL PHOSPHORUS REMOVAL


INFLUENT AND BYPASSRS Raw Sewage

EFFLUENTPLE Plant Effluent

INPLANT PIPINGPI Primary InfluentPE Primary EffluentML Mixed LiquorSE Secondary Effluent

SLUDGE AND BIOSOLIDSRAS Return Activated SludgeWAS Waste Activated SludgePSD Primary SludgeTPS Thickened Primary Sludge

LEGEND:

CHEMICALFACILITY

STRUVITEBUILDING

PO4 RELEASETANK

PRIMARYSLUDGEFERMENTATION

WEST BOISE WWTF: 24-mgdSCENARIO BK2F: EBPR W/ FERMENTATION + PO4 RELEASE + INTENTIONAL STRUVITE


TABLE 5 TMSBAS Capital Improvement Projects

Capital Improvement for TMSBAS Estimated Expense

Irrigation system for Twenty Mile South Farm Field 431 $200,000

Drill pipe fencing materials $400,000

Construction, repair and upgrade of structures and equipment $600,000

Equipment maintenance and part building $600,000

Total $1,800,000

Future Service Area Numerous combinations of wastewater management alternatives for the FSA were evaluated. A final alternative selection was not made during the evaluation process, but it was determined that wastewater management in the FSA should include wastewater reclamation and reuse during the irrigation season. Because of several technical and regulatory uncertainties, however, the disposal of wastewater during the non-irrigation season presents several challenges. The most likely non-irrigation season disposal options include either discharge to the ground using rapid infiltration or wetlands, or discharge to surface water such as Ten Mile Creek. However, both disposal options require that several technical and regulatory steps to be solved. Therefore, it is proposed that the following additional studies and evaluations be conducted in order to make informed decisions that support sustainable growth in the FSA as noted below:

Determine the viability of surface water discharge to Ten Mile Creek.

Determine the viability of discharge to irrigation canals.

Evaluate hydrogeologic and soil characteristics to determine the viability of wetland treatment and rapid infiltration options. This work can also be used to determine potential impact to wells and aquifer storage and recovery potential.

Maintain open communication lines with developers to anticipate wastewater treatment needs and discuss options during the planning process.

Continue to expand the TMSBAS to maintain sustainable land application rates of biosolids for future growth.

Figure 11 provides a chart illustrating these decisions and potential pathways. It was noted the preferred buildout model in the FSA is to provide a regional gravity sewer system with multiple satellite WWTFs along it for treatment of wastewater that is generated upgradient. The satellite WWTFs would provide treated wastewater for turf irrigation (landscapes, golf courses, open spaces, roadsides, and greenbelts). The upgradient WWTFs would be liquids-only treatment facilities wherein the solids generated from each satellite WWTF would be conveyed down the central gravity sewer to a single WWTF with solids treatment capability. The biosolids would be applied to agricultural land at the TMSBAS. The multiple satellite WWTFs alternative provides greater adaptability, flexibility, and phasing ability. In addition, each of the WWTFs could be phased incrementally by building modular treatment

BOI091560001.DOC/WBG050310052451BOI 39


process units of approximately 1 mgd, each. Figure 12 shows for the Multiple Satellite WWTF Option.

Implementation and Schedule for the Recommended Actions An overview of the timeframe for the additional planning actions and the recommended near-term actions are depicted in Figure 13. Planning actions include: (1) additional hydrogeologic and soils investigations to better understand the viability of creating wetlands with treated wastewater at the West Boise WWTF; (2) further exploration of the viability of utilizing the Phyllis canal as an acceptable discharge option; (3) determination of the viability and limitations of continued river discharge in the context of future low level phosphorus limitations, temperature discharge requirements, and phosphorus trading opportunities. These planning actions are expected to be completed over the next 3 years.

The timeframe for the recommended near-term actions at the Lander Street and the West Boise WWTFs are also depicted in Figure 13. These actions are expected to be completed over the next 5 years.

Cost Implications Cost for the recommended initial facilities actions (less than 5 years) is $44,600,000 as identified in Table 6. This could increase the cost of the average sewer bill by about $2.40 dollars per month.

TABLE 6 Cost of Near-Term Projects

Item Value

Warm Springs Trunk (Harris Lift Station and Force Main) $1,700,000

Lander Street Interceptor Repair or Replacement and Diversion for flow in/out of the Lander WWTF to the SBI

3,000,000

Sewer Rehabilitation ($800,000 per year for 5 years) $4,000,000

West Boise WWTF

Phosphorus Removal to 1.0 mg/L or Less $20,900,000

Combined Heat and Power Production with Digester Gas $3,500,000

Enhanced Digester Gas Production $400,000

Primary Clarifier Flow Restriction Improvements $5,300,000

UV Disinfection Reliability and Performance Improvements $4,000,000

Twenty Mile South Biosolids Application Site Improvements $1,800,000

TOTAL $44,600,000

*Construction cost will be estimated during the preliminary engineering phase.

Works Cited Lower Boise Watershed Council and Department of Environmental Quality. 2008. Lower Boise River Implementation Plan Total Phosphorus, Final. December.

40 BOI091560001.DOC/WBG050310052451BOI

Use Wetlands

Use RI Basins

All Trunk to WestBoise WWTF

To PhyllisCanal OK?

50% ReuseGoal

50% Reuse&/or 0.07 Enough

TP TradesAvailable?

Go to Satellite StrategyTo Phyllis Canal Trading

yes yes

nono

ReevaluateStrategy

EffluentTemperature Thermal

DischargeOK?

yes

no

Discharge to River, Highly Treated/Chilled ($$$)

Alternative Regulatory Solution

SatelliteTreatment: One

Plant & 5 Plants

WinterDischarge

To10-Mile Cr

OK?

ReuseHigh Demand &Value for Reuse

Water?

Reuse Locally

Reuse at TMSBAS

Wetland Seepage Good

WetlandSeepage?

To 10-Mile Creek

yes yes

yes

no

no

noSeepage

Acceptable? RecoveryFeasible &Affordable

?

Aquifer Recovery

No Aquifer Recovery

ReevaluateStrategy trategy

ReevaluateStrategy gy

Effluent Storage

Go to All Trunk Strategy

yes

no Go to All Trunk StrategyLand Available

to Expand TMSBAS?


FIGURE 11

FUTURE SERVICE AREA DECISION TREE

[Ú

3Q

3Q

3Q3Q

3QKuna Mora Rd.



3N2E

2N2E2N1E

3N1E

4N2E

2N3E

4N1E

3N3E

5N1E

1N1E 1N2E 1N3E

2N4E

5N2E

4N3E

3N4E

1N4E

Boise

Eagle

Meridian

Legend

S/SE Future Sewer Planning Area


Current Area Served

10 Mile Creek Drainage Ridgeline

Major Ridgelines


3Q Waste Water Treatment Plant

[Ú Lift Station

Proposed Sewer Trunks

18"

21"

24"

27"

30"

36"

42"

Existing Sewer Trunks

18 - 21"

21 - 27"

27 - 36"

36 - 48"

48 - 72"

0 15,000 30,0007,500

Note: Foothills limited buildableland use not reviewed


North


FIGURE 12

FIVE WWTFS FSA ALTERNATIVE

Planning Actions (~3 years)

Initial WWTF Actions (~5 years)

Lander St WWTF

• Keep it operational without major CIP

• Reduce load as WB capacity is firmed up

• Get permitted for discharge of sludges into SBI

• Construct facilities for transport of sludges to WB & discontinue digestion at LS

• Construct LS Flow Diversion facilities compatible both options

• Construct 42" LS Interceptor Replacement

Lander St WWTF

West Boise WWTF

• Convert to EBPR with Chem trim and struvite production

• Remove bottlenecks to obtain 24+/- mgd capacity

• Implement enhanced digester gas production and co-generation

• Optimize plant operation for SVI, nitrification & EBPR

• Pilot test chemical feed & filtration facilities for phosphorus removal

West Boise WWTF

Reevaluate monetary and non-monetary factors and decide WB effluent usage

• Explore optional uses for Lander St site

• Further evaluate financial impacts of write-off of LS assets

Optional Uses

Lander St WWTF

Write-Off

Other

• Refine the science/engineering temperature reduction and phosphorus removal

• Conduct insitu testing• Refine regulatory understanding

including pretreatment required

• Refine cost estimates• Conclusions: viability and

limitations

WB Effluent to Wetland

ning Actions (~3 years)(

engineeringion andalingnderstanding

ment

tesity and

land

• Explore with Pioneer Irrigation District (PID) & DEQ

• Treatment requirements

• What PID wants and contract terms

• Potential City and environmental benefits: clean drain discharges for P offset, water for domestic use

• Refine cost estimates

• Conclusions: viability and limitations

WB Effluent to Phyllis Canal

• Determine effluent temperature requirements

• Determine effluent phosphorus requirements

• Determine trading opportunities

• Refine cost estimates

• Conclusions: viability & limitations

WB Effluent to River


FIGURE 13

SUMMARY OF SHORT-TERM PLANNING AND INITIAL FACILITIES ACTIONS

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