Memorandum
City of Lawrence
Utilities Department
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TO: |
David L. Corliss – City Manager Cynthia Wagner - Assistant City Manager Diane Stoddard - Assistant City Manager |
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FROM: |
Nicholas Hoyt – I/I Manager |
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CC: |
Dave Wagner – Director of Utilities Mike Lawless – Deputy Director of Utilities Philip Ciesielski – Assistant Director of Utilities Beth Krishtalka – Assistant to Director |
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Date: |
May 7, 2014 |
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RE: |
Agenda Item – Execute Construction Contract for UT1415 Emergency Sanitary Sewer Repair (1000 Block of Connecticut Street) |
Background/Project Description
In the alley between the 1000 block of New York and Connecticut Street, there is a parallel 48 inch brick storm sewer adjacent to an 8 inch VCP sanitary sewer. The sewers were constructed in approximately 1932 at similar flow line elevations and with less than 2 feet of horizontal separation. The City recently discovered sanitary sewer service connections passing through the storm sewer to connect to the sanitary sewer as shown in the attached map. The service connections are broken in the storm sewer causing sanitary flow to discharge into the storm sewer. This causes a cross connection between the two sewers. There are 6 houses directly connected to the storm sewer and four cross connections locations.
Staff released an RFQ to contract with a qualified project team for professional design and construction services to complete the emergency repair. A total of 6 submittals were received from general contractors with professional engineer sub-consultants. After reviewing each proposal, Public Works and Utilities Department staff unanimously selected the Emery Sapp and Sons, Inc. project team with BG Consultants as the design engineer. The selection was based on the submitted hourly labor rates, experience with similar projects, and the availability of resources.
Project Status
Public Works and Utilities Department staff discussed a large number of possible options to complete the repair with the project team. The possible options discussed included storm sewer repairs/replacement, sanitary sewer repairs/replacement, residential injector pumps to lift domestic sanitary flow over the existing storm sewer, several combinations of sewer lining repair methods and other trenchless repair techniques. After reviewing construction feasibility, O&M requirements, and capacity requirements of each option, the following alternatives were reviewed in detail:
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Alternative Number |
Sanitary Sewer |
Storm Sewer |
Comments |
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1 |
Replace along existing alignment, change elevation. |
Leave in place, repair service crossings. |
Requires excavation and tunneling around existing brick storm sewer. Structural integrity of storm sewer likely to be compromised during construction. |
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2 (Recommended) |
Replace along new alignment, change elevation. |
Replace with 34" x 53" elliptical concrete pipe |
New storm and sanitary sewer. Future repairs unlikely. |
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3 |
Leave in place, repair and reconnect service connections. |
Replace with 34" x 53" elliptical concrete pipe |
Substantial investment to replace storm sewer. Aging sanitary sewer left in place under new storm. Difficult future sanitary repairs possible. |
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4 |
Construct new sanitary to the west of existing storm sewer. |
Leave in place, repair service crossings. |
Requires excavation next to existing brick storm sewer. Structural integrity of storm sewer likely to be compromised during construction. |
Staff is recommending proceeding with Alternative 2 material acquisition and preliminary engineering services. The project team agreed that completing sanitary sewer construction directly adjacent to the brick storm sewer was extremely uncertain due to the unknown structural strength of the 80 year old storm sewer. This uncertainty eliminated Alternative 1 and Alternative 4. Alternative 3 was unacceptable for staff because the maintenance and possible repairs of the existing sanitary sewer would be difficult after a new storm sewer was built above it.
Project Schedule
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City Commission Approval to Advertise RFP |
March 25, 2014 |
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Responses to RFP Due |
April 4, 2014 |
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Commission Authorization |
May 13, 2014 |
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Final Project Completion |
July 15, 2014 |
Project Funding
The preliminary cost estimate for this project is currently $450,000. Staff and the project team are currently gathering pertinent data for planning purposes and evaluating project details, including site restoration, residential service lateral replacements, materials and construction methods. The project will be funded by the 2013 bond allocation.
Action
Authorize staff to proceed with preliminary engineering services and material acquisition with the Emery Sapp and Son, Inc./BG Consultants project team for UT1415 Emergency Sanitary Sewer Repair (1000 Block of Connecticut Street). Authorize staff to execute a contract based on a time and materials budget.
Thank you for your assistance. Please advise if you have any questions.