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West Interceptor – Spring Street Relief Project Business Case ID: B04

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West Interceptor – Spring Street Relief (Lining Project)

Project Purpose: The purpose of this project is to correct condition defects and extend the service life of the West Interceptor (WI) – Spring Street Relief between Randall Avenue and West Washington Avenue in the City of Madison (see yellow highlighted line on map above). The project also includes the rehabilitation of a small portion of the West Interceptor in the vicinity of West Washington Avenue. Project Proposer/Champion: Todd Gebert Department: Engineering Project Involvement: The Engineering Department will provide overall management of the project, including preparation of plans and specifications, contract administration, and construction management.


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Project History and Status: The WI‐Spring Street Relief was constructed in 1940 and consists of 4,580 feet of 24” cast iron sewer. Approximately 1,300 feet of sewer on Spring Street was inspected by closed‐circuit television in 2011 prior to a street reconstruction project. This section of sewer shows evidence of moderate to severe tuberculation. Tuberculation is the buildup of deposits on the inside walls of the pipe due to chemical reactions between the wastewater and the cast iron pipe. The deposits generally form above the normal waterline and their effect is to decrease the carrying capacity of the sewer by reducing the effective diameter of the pipe and increasing the surface roughness. Tuberculation may also compromise the structural integrity of the pipe if left unchecked. CARPC’s MMSD Collection System Evaluation (2018) projected that additional capacity is not needed in the WI‐Spring Street Relief before the year 2040. A summary of peak flows in sections of the Spring Street Relief Sewer is shown below for various time increments.

This project also includes the rehabilitation of approximately 590 feet of 24” cast iron sewer along the original West Interceptor from manhole MH02‐001 to manhole MH02‐003. This stretch of sewer was originally within the limits of the 2017 rehabilitation project for the West Interceptor but was removed and included with this project in order to minimize costs for flow bypassing and disruption to traffic in West Washington Avenue near Pump Station 2. Options:

a. Description: The WI‐Spring Street Relief consists of cast iron pipe that is 79 years old. The section televised along Spring Street in 2011 shows moderate to severe areas of corrosion along its length. It has reached the end of its useful life and is in need of rehabilitation or replacement to address corrosion of the interior pipe surface. Capacity upgrades are not deemed necessary prior to the year 2040.

MH02‐316 MH02‐314A 443 24 6.54 1.73 26% 1.14 17% 1.60 25% 1.61 25% 1.62 25% 1.63 25% 1.64 25%

MH02‐314A MH02‐306A 2,437 24 6.54 2.59 40% 2.09 32% 2.67 41% 2.73 42% 2.78 43% 2.84 43% 2.90 44%

MH02‐306A MH02‐300 1,697 24 6.54 3.59 55% 2.96 45% 3.77 58% 3.82 58% 3.88 59% 3.94 60% 4.00 61%

MH02‐300 MH02‐101 3 24 6.54 8.33 127% 7.47 114% 9.11 139% 9.26 142% 9.40 144% 9.55 146% 9.70 148%

Junction with Old West Interceptor (Table 4‐27)

From To

Length

(ft)

Pipe

Dia.

(in)

Nominal

Capacity

(mgd)

Peak Flows (mgd) / Percent Nominal Capacity

2010 2015 2020 2025 2030 2035 2040


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b. Alternatives

Alternative 1 – Rehabilitate the existing sewer with a cured‐in‐place liner Under this alternative the 24” cast iron pipe will be rehabilitated with a cured‐in‐place liner. All manholes older constructed before 1970 will also be lined as part of the rehabilitation (see attached Figure 1). Alternative 2 – Construct a new sewer with open cut excavation This alternative consists of constructing a replacement sewer parallel to the existing sewer. The majority of the existing sewer is located along busy local streets in downtown Madison and involves crossings of standard arterial streets (i.e. Regent Street and Park Street). Alternative 3 – Do nothing Under this alternative the existing sewer would not be rehabilitated or replaced. Due to the age of the sewer and the condition defects present, this alternative is not considered feasible and was not advanced for further economic analysis.

c. Key Risks and Issues

Alternative 1. Rehabilitation of the existing sewer with a cured‐in‐place liner will cause minimal disruption to the environment and neighborhood. Bypassing of wastewater around the sections to be lined will be required during insertion of the liner. Due to its close proximity with the West Interceptor and the West Interceptor–Randall Relief sewers and the relatively few direct connections of laterals and local mains, bypassing of the Spring Street Relief Sewer should be fairly straightforward. Due to the small number of direct connections to the interceptor, lining will cause only minor disruption to a small number of users during the installation process as lateral connections will be temporarily removed from service. These service outages will be limited in duration and will not result in great inconvenience to the user. The interceptor is generally located within the public right‐of‐way, with some stretches running in the terrace (i.e. between the curb and right‐of‐way line). There is sufficient access to manholes for lining operations.

Alternative 2. Construction of a replacement sewer with open cut excavation will cause significantly more disruption as compared to Alternative 1. The


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existing sewer was installed in 1940 and for much of the route the sewer is located in the terraces of the public right‐of‐way, suggesting that the public right‐of‐way corridor is heavily congested with existing utilities. It will likely be difficult (and costly) to find a suitable route for a replacement sewer along this corridor. In addition, construction of a replacement sewer along the existing route will cause significant disruption to vehicular and pedestrian traffic as well as to residents and businesses in the downtown area.

d. Economic Analysis Please see the attached 50‐year life cycle cost estimate. A summary of present worth costs is provided in the following table:

Capital Cost O&M Cost Salvage Value

Total Present Worth

Alternative 1 $1,844,000 $61,000 $6,000 $1,834,000

Alternative 2 $4,850,000 $61,000 $294,000 $4,617,000

Recommended Option Staff recommends Alternative 1 due to its cost effectiveness and its overall ability to better meet the triple bottom line relative to Alternative 2. Rehabilitation of the sewer with a cured‐in‐place liner will cause significantly less disruption to the environment, traffic and neighborhood than construction of a replacement sewer by traditional open cut excavation. Project Schedule:

Start Date Completion Date

Planning June 2014 December 2018

Design June 2019 March 2020

Bid Date April 2020 May 2020

Construction June 2020 August 2020

Financial Summary (2019 dollars):

Total Project Cost

District Staff $190,000

Contractor $1,600,000

Total $1,790,000


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Fiscal Year Allocation (2019 dollars):

2019 2020

District staff $55,000 $135,000

Construction $0 $1,600,000

Total $55,000 $1,735,000

Note: Numbers will be modified by an inflation factor to bring them to the proper year’s cash allocation within the Capital Budget.

Fiscal Year Allocation (In current year or future year dollars):

2019 2020

District staff $55,000 $140,000

Construction $0 $1,650,000

Total $55,000 $1,790,000

Madison MetropolitanSewerage District

Prepared by: TWG

Date: 2/5/16FIGURE 1: West Interceptor & West Interceptor -

Spring Street Relief (Lining Project)

Spring Street Relief Sewer

West Interceptor

Existing MMSD Interceptor

Pump Station 2 0 200 400

Feet

Regent St

Spring StMH02-316

MH02-300

MH02-101

MH02-003

50‐YEAR PRESENT WORTH COST ANALYSIS

FOR WEST INTERCEPTOR ‐ SPRING STREET RELIEF AND WEST INTERCEPTOR

Present‐Worth Analysis Year 2019

Analysis Period (yrs) 50

End of Analysis Year 2069

Cost in Year 2019 Present 2019 Present Year 2019 Present Total 2019

Project Description Year Constructed Worth Worth 2069 Worth Present Worth

Alternative 1 ‐ Rehabilitate existing sewer

Install cured‐in‐place pipe and manholes 2020 1,844,000 1,779,000 61,000 37,000 6,000 1,834,000

Alternative 2 ‐ Replacement sewer

Replacement sewer 2020 5,026,000 4,850,000 61,000 1,742,000 294,000 4,617,000

Assumptions and Notes:

(1). Base interest rate = 3.63%

(2). Construction cost escalation rate = 3.00%

(3). Interceptor & Forcemain Service Life (yrs) = 75

(4). Pipe liner life (yrs) = 50

(5). Annual O&M interceptor cost ($/ft) = 0.25

(6). Annual O&M forcemain cost ($/ft) = 0.25

Capital Cost Salvage ValueO&M Costs

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CAPITAL COSTS FOR WEST INTERCEPTOR ‐ SPRING STREET RELIEF AND WEST INTERCEPTOR

2019 2019

Estimated Unit TotalNo. Description Footnote Quantity Units Cost Cost

Alternative 1 ‐ Rehabilitate existing sewer with cured‐in‐place liner

Mobilization 1 L.S. $50,000 $50,00024" cured‐in‐place liner (4) 4,670 L.F. $105 $490,350Rehabilitate manhole 28 EACH $4,500 $126,000Flow bypassing 1 L.S. $345,000 $345,000Reinstate services 5 EACH $500 $2,500Tuberculation removal (3), (4) 4,670 L.F. $27 $126,090Access for tuberculation removal 1 L.S. $200,000 $200,000Traffic control 1 LS $50,000 $50,000

Sub‐total $1,389,940Contingencies 15.0% $208,491

Construction Total $1,600,000Engineering 12.0% $190,000

2019 Project Total $1,790,0002019 Project Total $1,790,000

Alternative 2 ‐ Replacement sewer

Replace 24" sewer (Spring Street Relief and West Interceptor) (2), (4) 5,165 L.F. $945 $4,881,000

2019 Project Total $4,880,0002019 Project Total $4,880,000

Notes:

(1). All unit costs in 2019 dollars.

Capital Costs for West Interceptor ‐ Spring Street Relief & West Interceptor

(2). Unit price taken from MMSD's 50‐year Master Plan with increase of 5.4% per annum. Surcharge of 25% added to unit price to adjust for congested utility

corridor, traffic conditions and crossing of three larger storm box culverts.

(3). Assume drag scraping or some similar technology will be required to remove tuberculation from cast iron pipe.

(4). Includes approximately 4,082 feet of West Interceptor/Spring Street Relief from MH02‐300 to MH02‐316 and 588 feet of West Interceptor from MH02‐001 to

MH02‐002.

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