6. Alternatives Analysis, Onondaga Lake Improvement

Harbor Brook CSO Abatement Project Facility Plan (Aug 2005)
by Brown and Caldwell
for Onondaga County Dept of Water Environment Protection

6. Alternatives Analysis

6.1 Introduction

This section covers, the specific application of each technology, the basis for design and project cost estimates, and how these alternatives relate to basin-specific options. This section also summarizes the alternatives for the Upper, Middle, and Lower Basins. The CSO abatement scenarios that address all three basins are discussed in Section 7 of this report.

It should be noted that all project cost estimates assume that any new conveyances would be constructed within the public right-of-way. Costs do not include potential hazardous waste remediation that may be required at a site.

6.2 Sewer separation

Separation of sanitary and stormwater systems is considered a viable option for CSO abatement due to the elimination of the sewage content from the discharge to the Brook and to the Lake.

Description: Based on the anticipated extent of disruption, duration of construction and the high project cost of separating large densely urban tributary areas, sewer separation is considered viable for the Middle Basin of Harbor Brook (CSOs 005, 006, 006A, 007, 008, 009, 010, 011, and 013). The characteristics of the Middle Basin which make it more viable to receive sewer separation include: fewer number of streets and smaller volumes of CSO. For comparison purposes, sewer separation of the entire Harbor Brook Basin is presented as Scenario 1 in Section 7 of this report.

Basis of Design: For cost comparison purposes, sewer separation would include: the installation of a new, deeper sanitary sewer sized to accommodate dry-weather flow; the replacement of the laterals to the property line; the conversion of the existing combined sewer into a storm sewer, limited work on private property; lead and galvanized water service replacement; and milling and overlay of the top course of pavement of the full width of the street. The construction costs would increase if the existing combined sewers require replacement or rehabilitation to convert them to storm sewers.

Construction sequencing and project scheduling: It is estimated that the separation of the almost 22,000 lf of combined sewers along the covered section of Harbor Brook would require approximately 6 years. It is estimated that the conceptual design and the environmental review process would require 12 months. If the areas to be sewer separated were divided into different projects, it would minimize disruption to the community. For example, the design and bidding of the first project (CSOs 006, 008, 009 and 013) could be completed in approximately one year, with construction being completed in a two-year period. Design and bidding of the second project (CSOs 005, 007 and 011) could overlap construction of the first group, with construction of the second commencing one year following the first and being completed three years following the first. Similarly, for the remaining sewer-service areas, (CSOs 006A and 010) the design and bidding would overlap with construction of the second. Construction of the third would commence one year following the second and would be completed at the same time as the second.

Permitting requirements: It is anticipated that the existing SPDES permit would require modification upon completion of this project.

Estimated Cost: The costs for sewer separation for each CSO tributary area were based on the lengths of the combined sewers in each drainage area gathered from collection system maps and an estimate of the ratio of residential and commercial property based on aerial photography from each tributary area. The sewer lengths and estimated costs are summarized in Table 6.1.

The estimated project cost for sewer separation of the drainage areas tributary to CSOs 005 through 008 is $8,750,000. The project cost for the sewer separation of the drainage areas tributary to CSOs 009 through 013 is estimated to be $16,270,000. The estimated project cost for sewer separation of the entire Harbor Brook CSO areas is $259,610,000. The details of the costs are described in Section 5.3 and summarized in Table 6.1.

Table 6.1 Estimated Project Cost for Sewer Separation Lower Basin
Drainage area	Est. length of combined sewers (linear ft)	% residential	% commercial	Est. construction cost of sewer separation
063	19,964	100	0	$14,968,000
003	24,138	74	26	18,077,000
004	47,844	100	0	35,870,000
Lower Basin Subtotal: $68,915,000

6.3 Conveyance to Metro

Two alternatives have been identified for conveyance of Harbor Brook CSOs to Metro for treatment: namely, conveying CSOs 003 through 008, or full conveyance (CSOs 003 to 078). For both alternatives CSO 063 would receive an FCF.

6.3.1 Full conveyance

Description: This alternative would consist of a conveyance that will divert flow from each of the 18 Harbor Brook outfalls to Metro for storage/treatment. To meet the ACJ requirements, an additional storage facility would need to be provided to capture the 1-year recurrence interval volume. Additionally, a new pump station would be required.

It has been assumed for these analyses that the Metro tertiaries may become available in 2004 and could be utilized for the additional storage required. Stored CSO from the storage facilities would be pumped to the Metro headworks for treatment when capacity became available. Flows in excess of the combined storage volume would be conveyed to a separate tank and receive high-rate disinfection before discharging to the Lake. As such, the Metro tertiaries and new disinfection facility will act as an Overflow Retention Facility (ORF). The Metro tertiaries would require retrofitting to be utilized for this purpose. The detailed evaluation of the required upgrades to the Metro tertiaries has been made.

Click here for Appendix D. Pump to Metro alternative evaluation.

Basis of Design: The new conveyances would be sized to transport the combined sewage from all 18 CSOs associated with the 1-year design storm. The new pump station would be designed to convey CSO to the Metro tertiaries at a flow rate of 200 cfs. This is the hydraulic capacity of the existing piping to these facilities. The estimated cost for the Metro retrofit is described in Appendix D. The estimated project cost for this alternative also includes the required pump station and ORF components.

Construction sequencing and project scheduling: It is estimated that a period of 18 months will be required for design, environmental review, and bidding and a minimum of 36 months for construction and start-up.

Permitting requirements: It is anticipated that the existing SPDES permit would require modification upon completion of this project. A Highway Work Permit will be required from NYSDOT for the crossing of I-690, and potentially for other work along state owned roadways.

Estimated Cost: The project cost for the collection and conveyance of all Harbor Brook CSOs to Metro and for the upgrade to Metro for treatment, is $108,300,000.

6.3.2 Lower basin conveyance

Description: The CSOs located in the Lower Basin (CSOs 003 and 004) as well as a portion of the Middle Basin CSOs (005, 006, 006A, 007, and 008) could be conveyed to a pumping station and to the Metro tertiaries for storage and subsequent treatment. The results of the Bacterial Model indicate that to meet the bacterial requirements of the ACJ, at a minimum CSOs 003 and 004 would have to be collected and conveyed to Metro. Wet-weather volumes greater than the 1-year recurrence interval volume would be discharged through the existing overflows and/or at the new pump station outfall.

Basis of Design: The new conveyances would be sized to transport the combined sewage from the Lower Basin CSOs associated with the 1-year design storm. The basis for design for storage is the volume required to capture the 1-year recurrence interval volume from the Lower Basin CSOs. It has been determined that the Metro tertiaries will be sufficient to store this volume for subsequent treatment at Metro. The equalization storage will be approximately 860,000 gallons, based on the influent hydrograph for the 1-year design event and a pumping rate of approximately 150 cfs. This flow rate would accommodate the addition of the peak design flow from the Kirkpatrick St. Pump Station (KSPS). If the KSPS is not directed to this system, the Lower Basin PS and the force main to Metro could be sized for the hydraulic capacity of the existing tertiary piping. This capacity is approximately 200 cfs.

This alternative includes the conveyances as described, the new pump station and the required upgrades to the Metro tertiaries. The assessment of the necessary upgrades to the Metro tertiaries is described in a technical memorandum entitled: Pump to Metro Alternative Evaluation and is provided in Appendix D of this report.

Construction sequencing and project scheduling: As a part of the upgrades to Metro, currently under construction, the existing tertiary tanks will become available by 2004. Project design and bidding, and the construction of the conveyances and Lower Basin PS would require approximately three years.

Permitting requirements: A Highway Work Permit will be required from NYSDOT for the force main crossing of I-690, and potentially for other work along state-owned roadways.

Estimated Cost: The project cost for the collection and conveyance of CSOs 003 through 008 to Metro, including upgrades to Metro, is $58,880,000.

6.4 Regional treatment facilities (RTFs)

Based on the location of the major CSOs and the characteristics of suitable local sites, it would be practical to construct two separate regional treatment facilities (RTFs) in the Harbor Brook combined-sewer basin. The first, identified as the Upper Basin RTF, would address the Upper Basin CSOs and could be designed to address a portion of the Middle Basin. The second facility, the Lower Basin RTF would provide CSO abatement for the Lower Basin and could be designed to address a portion of the Middle Basin as well. The details of these sub-alternatives will be described in the next sections.

Three technologies that would provide storage-treatment technologies in combination with disinfection are considered viable for the design of these RTFs. These include, an overflow retention facility (ORF) as described in Section 3.2.2.7, a vortex-disinfection facility, as described in Section 3.3.3, a regional storage facility as described in Section 3.2.2.6, and a combination of vortex-disinfection and off-line upstream storage.

The vortex-disinfection facility will hereinafter be referred to as a High Rate Treatment (HRT) facility. It should be noted that an ORF would need to provide high-rate disinfection to the flow before discharge when the detention tank capacity has been met and additional CSO occurs beyond the capacity of the system. It should also be noted that each of the facilities would provide a level of storage with subsequent CSO treatment at Metro.

An Overflow Retention Facility (ORF) would provide capture of the CSO generated from the 1-year, 2-hour design storm. The CSO would be pumped to Metro for treatment at the conclusion of the storm or when capacity becomes available. The removal of floatables and solids would need to be performed by screens upstream of the retention tank.

If an HRT facility is used, CSO up to the 1-year, 2-hour design storm would be conveyed to the RTF for the removal of solids and floatables, followed by high-rate disinfection and subsequent discharge of treated flows to the Brook when necessary. Concentrated underflow from the vortex would be pumped into the HBIS for subsequent treatment at Metro. The storage volume within each of these facilities (ORF or HRT) would provide CSO from a majority of storm events to be completely captured and conveyed to Metro. Storms beyond the 1-year design would receive some level of solids removal and be disinfected.

If a regional storage facility is used, CSO would be captured and stored for up to the volume calculated based on a 1-year recurrence interval as determined from long-term simulation. The regional storage facility would not discharge CSO in an average rainfall year. However, during larger storm events (less frequent than once per year), the facility would discharge CSO that would not receive disinfection. Also, if the storage is full (from a 1-year storm), then any immediately following storm would be discharged untreated unless the storage is emptied to store that storm volume.

An additional alternative was considered which includes a facility with off-line upstream storage vortex-disinfection. This alternative includes smaller (half-size) vortex-disinfection facilities with upstream storage to reduce peak influent flow to the vortex and disinfection. The facilities are sized based on the 1-year, 2-hour design storm.

A common project associated with each scenario regardless of the technologies considered is the replacement of the upper and middle basin portions of the HBIS. The HBIS from CSO 017 to CSO 014 is a 30-inch slab top sewer built in the early 1900s and is in poor condition. See Figure 6.1 for a typical cross-section from the as-built drawing.

Figure 6.1. Typical Cross-section of the HBIS near Fowler HS

In addition, in the vicinity of Fowler High School, the HBIS appears to have a significant limitation that has reduced its capacity by more than 50%. The County has tried on numerous occasions to identify the defect. No obstruction has been identified; the interceptor may have experienced differential settlement. As a result of these conditions, the HBIS should be replaced in-kind from Velasko Rd. north to Fayette Street.

The Upper Basin RTF will include abandonment of the HBIS and utilization of the new conveyance pipeline to convey dry weather flow to the RTF location. Separate costs are included for the HBIS replacement in the Middle Basin from Delaware to Fayette Street. The estimated project costs for the replacement is $2,340,000.

6.4.1 Upper Basin RTF

Description: CSOs 014 through 078 must be stored-treated at this facility to meet the requirements of the ACJ. The facility could be designed to address CSOs 009 through 013 as well. The degree of CSO pumping which will be required depends on the CSOs conveyed to the facility and the site chosen.

Basis of design: For an HRT facility, the CSO transmission lines, equalization storage, lift station (or pumping station and force main depending on the site selected), vortex unit and the disinfection tank would need to be sized to accommodate the peak 1-year, 2-hour design storm overflow rate from the CSOs included in the collection area. These range from 175 cubic feet per second (cfs) for the larger facility (CSO 009-078) to 155 cfs for the smaller facility (CSO 014-078).

For an ORF, all of the above components would be included and sized similarly. However, a retention tank would be used in place of the vortex units. The facility would need to be sized to capture the volume of CSO generated by the 1-year, 2-hour design storm. Volumes in excess of this would receive disinfection and would be discharged to the Brook. Captured CSO would be pumped back to the HBIS for subsequent treatment at Metro. The total storage volume required for the ORF would be 3.4 MG (only considered for CSOs 014-078). For comparison purposes, the HRT facility would provide a total facility volume of approximately 0.6 MG of storage.

For an off-line upstream storage and vortex-disinfection facility, the storage volume is 0.9 MG. This is the volume that is needed to reduce the vortex-disinfection to one-half of the full vortex-disinfection alternative. Captured CSO would be pumped back to the HBIS for subsequent treatment at Metro.

The regional storage volume would include 8.2 MG determined based on long-term simulation results. Captured CSO would be pumped back to the HBIS for subsequent treatment at Metro. Volumes in excess of this would be discharged to the Brook without disinfection. Initial evaluation of the HBIS capacity has determined that the HBIS would not have the capacity to dewater the volume associated with Upper Basin regional storage within a 48-hour period following the storm event. This assumes the HBIS improvements discussed previously are implemented.

Construction sequencing and project scheduling: It is estimated that the Upper Basin RTF would require approximately 18 months for environmental review, design and bidding and approximately 30 months for construction and start-up.

Permitting requirements: It is anticipated that the existing SPDES permit will require modification upon completion of this project.

Disadvantage: The community disruption during construction along the routes of the conveyances (generally along the HBIS from Velasko Road to Fayette Street): The disruption can be reduced by constructing FCFs for CSOs 009, 010 011 and 013.

Estimated Cost: The estimated project costs for the facilities described above are shown in Table 6.2.

Table 6.2. Summary of alternative costs
Alternative	Project cost $000,000
Upper Basin vortex	$24.60
Upper Basin vortex with offline-upstream storage	28.61
Upper Basin ORF	32.30
Upper Basin regional storage	N.A.*
Lower Basin vortex	21.11
Lower Basin vortex with offline-upstream storage	24.45
Lower Basin ORF	28.77
Lower Basin regional storage	29.81
*Dewater capacity not available in HBIS Note: Project cost includes escalation to midpoint of construction. Contingency and engineering, legal, and admin costs do not include connecting the Middle basin CSOs.

6.4.2 Lower Basin RTF

Description: At a minimum, CSOs 003 and 004 must be conveyed to the Lower Basin RTF to meet the requirements of the ACJ. The facility could be enlarged to accommodate flow from CSOs 005 through 008 from the Middle Basin. Similar to the Upper Basin RTF, several sub-alternatives exist for the Lower Basin RTF alternative.

Basis of Design: For an HRT facility, the CSO transmission lines, equalization storage, lift station (or pumping station and force main depending on the site selected), vortex unit and the contact tank would need to be sized to treat and discharge the peak 1-year, 2-hour design storm overflow rate from the CSOs included in the collection area. This peak rate ranges from 205 cfs for the larger facility (CSO 003 to 008) to 190 cfs for the smaller facility (CSO 003 to 004).

For an ORF, all of the above components would be included and would be sized similarly. However, a detention tank would be used in place of the vortex units and would be sized to capture the volume of CSO generated from a 1-year, 2-hour design storm. Volumes in excess of this would receive disinfection and would be discharged to the Brook. Captured CSO would be pumped back to the interceptor sewer when capacity becomes available. The required size of storage for the facility would be 3.7 MG (only considered for CSOs 003-004). For comparison purposes, the HRT facility would provide approximately 0.8 MG of storage.

For an off-line upstream storage and vortex-disinfection facility, the storage volume is 1.2 MG. This is the volume that is needed to reduce the vortex-disinfection to one-half of the full vortex-disinfection alternative. Captured CSO would be pumped back to the HBIS for subsequent treatment at Metro.

The regional storage volume would include 5.4 MG determined based on long-term simulation results. Captured CSO would be pumped back to the HBIS for subsequent treatment at Metro. Volumes in excess of this would be discharged to the Brook without disinfection.

Construction sequencing and project scheduling: It is estimated that for either type of technology, the Lower Basin RTF would require 18 months for environmental review, design and bidding and 30 months for construction and start-up.

Disadvantage: The disruption to the community during construction along the routes of the conveyances, generally along the HBIS from Lakeview Ave to the vicinity of State Fair Blvd.

Estimated Cost: The estimated project cost for the facilities described above are shown in Table 6.2.

6.5 Floatables control facilities (FCF)

Description: Based on the ACJ requirements, Floatables Control Facilities (FCFs) are not a viable treatment alternative for certain CSO discharges in the Harbor Brook sewershed area. FCFs have been presented as viable alternatives for relatively smaller CSOs, namely, CSO 005, 006, 006A, 007, 008, 009, 010, 011 and 013.

Since CSO 063 does not discharge directly from the sewer to the Brook, it has been assumed that an FCF will be sufficient treatment for this CSO. This facility will hereafter be referred to as the Emerson FCF. Several of the scenarios presented in the next section include the Emerson FCF.

There are four technologies that are considered viable for floatables removal: underflow baffles, mechanically cleaned oscillating screens, net bags, weir-mounted mechanical screens, and manually cleaned screens. The technology chosen will depend on the site-specific conditions such as the size of the collection area, the peak flow rate, the frequency of activation, and the sensitivity of receptors in the site area.

For planning purposes it has been assumed that weir-mounted mechanical screens will be used at each FCF site with the exception of CSO 006 and 008. This technology has the highest project cost of the floatables control technologies evaluated. Detailed evaluation of the application of these screening technologies to the specific overflows will be left for the design phase of the project, as appropriate. CSO 006 and 008 will be eliminated by improvements to the regulator sewers as well as the Sacket Street and Richmond Avenue pumping stations.

Basis of Design: The FCF would be designed to accommodate the peak overflow rate generated by a 1-year, 2-hour design storm. This estimated cost represents a vaulted facility equipped with a mechanically cleaned, weir-mounted screen sized for an individual CSO.

Construction sequencing and project scheduling: It is expected that the smaller FCFs could be constructed in a much shorter time period than the RTFs. It is estimated that these facilities would require 18 months for design, environmental review and bidding and 12 months for construction and start up.

Permitting requirements: It is anticipated that the existing SPDES permit would require modification upon completion of this project.

Estimated Cost: The project cost of the Emerson FCF is $749,000. The costs of each individual remaining FCF within the Middle Basin are estimated at $513,000.

6.6 Summary of basin-specific options

6.6.1 Upper Basin

6.6.1.1 CSOs

The CSOs that have been identified in the Upper Basin are listed in Table 1.1 with associated peak overflow rates and overflow volumes. It should be noted that the total peak overflow rates shown in Table 1.1 do not take into account the attenuating effects if CSOs are combined into alternatives. This portion of the Brook is characterized as open channel and extends from the detention basin near Velasko Road to DePalma Ave.

6.6.1.2 Viable technologies and sites

The suitable sites are indicated based upon the site analysis information provided in Section 4. The following technologies are considered viable for CSO abatement in the Upper Basin:

Sewer Separation: Only alternative considered for Upper Basin is part of total sewer separation for entire Harbor Brook service area.

Convey to Metro: Part of an alternative whereby CSO from all of the basin would be conveyed to Metro

Convey to the Upper Basin RTF: The Upper Basin RTF would accommodate the Upper Basin CSOs (014 to 078) and could be designed larger, so as to address a portion of the Middle Basin CSOs as well (009 to 078). Suitable sites for this RTF are Site #10 or #11.

6.6.2 Middle Basin

6.6.2.1 CSOs

The Middle Basin of Harbor Brook has been identified as containing the covered section of the Brook, except for a small stretch of open channel near Fowler High School. This corresponds to the area between Delaware Street and State Fair Boulevard. The CSOs that have been identified in the Middle Basin are listed in Table 1.1 with associated peak overflow rates and overflow volumes. It should be noted that the total peak overflow rates shown in Table 1.1 do not take into account the attenuating effects if CSOs are combined into alternatives.

6.6.2.2 Viable technologies and sites

The following technologies are considered viable for CSO abatement in the Middle Basin:

Sewer Separation: Several alternatives consider sewer separation for all or portions of the Middle Basin.

Convey to Metro: Part of an alternative whereby CSO from all or a portion of the basin are conveyed to Metro. Conveyance of CSOs 005 through 008 to Metro is part of an alternative that would convey the Lower Basin CSOs 003 and 004 as well. The suitable site for the pump station is Site #4.

Convey to the Upper Basin RTF: This would convey CSOs 009 through 013 to the Upper Basin RTF. CSO pumping may be required, depending on the site chosen for the facility. The most suitable sites for the RTF are Site #10 or #11.

Convey to the Lower Basin RTF: CSOs 005 through 008 would be conveyed to the Lower Basin RTF combined with the Lower Basin CSOs. The suitable sites for the Lower Basin RTF is Site #4.

FCFs are considered for up to eight CSOs.

6.6.3 Lower Basin

6.6.3.1 CSOs

The Lower Basin CSOs have been identified and are listed in Table 1.1 with the associated peak overflow rates and overflow volumes. It should be noted that the total peak overflow rate do not take into account the attenuating effects if CSOs are combined into alternatives. The Lower Basin portion of the Brook begins at State Fair Boulevard and ends at Onondaga Lake. It is characterized as an open channel.

6.6.3.2 Viable technologies and sites

The suitable sites are given based upon Site Analysis in Section 4. The following technologies are considered viable for CSO abatement in the Lower Basin:

Sewer Separation: Has only been considered for the Lower Basin as part of full sewer separation of the entire Harbor Brook service area.

Convey to Metro: This was evaluated as part of an alternative whereby CSO from a portion of the lower basin would be conveyed to Metro. It has also been considered to convey CSOs 003 through 004 to Metro along with CSOs 005 through 008 from the Middle Basin. A suitable site for the pump station is Site #4.

Convey to the Lower Basin RTF: This alternative would convey CSOs 003 and 004 to the Lower Basin RTF. Additionally, this facility could be designed to provide CSO abatement to several Lower Basin CSOs. The suitable site for the Lower Basin RTF is Site #4

FCF: An FCF is being considered at CSO 063. Site #15 is a suitable location for this facility.