Title
Resolution - A Resolution Approving a Change Order to the National Parkway Contract for Additional Work Required to Cross Two Existing Gas Transmission Mains for an Amount not to Exceed $161,514.67 (Street Bond Fund)
Requested Action
The approval of a change order to the National Parkway contract for additional work required to cross two existing gas transmission mains.
Recommendation
The Engineering Staff recommends the approval of a change order in the amount of One Hundred Sixty One Thousand Five Hundred Fourteen and 67/100 Dollars ($161,514.67) to the National Parkway Contract for additional work required to cross two existing gas transmission mains.
Description/History
During the design of the project it was known that the two gas lines were shallow and could present potential construction problems with the new roadway and box culvert storm drain. City staff worked closely with the design engineer and with the pipeline companies to ensure that the design would meet the gas pipeline minimum clearances. The storm drain system was lowered under the gas lines and the street was raised over three feet from the natural ground to maintain acceptable clearances. The project was bid with the assumption that the storm drain could be installed by open cut and that the fill for the roadway could be placed with standard compaction equipment. It was not until our contractor was onsite coordinating with the gas line inspectors that several new and unforeseen costly construction methods were going to be required to construct the crossing. Lowering the lines was considered even during design, but that cost could exceed $400,000 per line. After several meetings with the gas line representatives, engineers and contractors it was concluded that the best and most cost effective option would be to tunnel the storm drain under the gas lines and place flowable fill over the gas lines and under the new pavement to avoid impacts from compaction equipment.
Staff is recommending approval of a change order in the amount of One Hundred Sixty One Thousand Five Hundred Fourteen and 67/100 Dollars ($161,514.67) to the National Parkway Contract for additional work required to cross two existing gas transmission mains.
Justification
The project cannot be completed without crossing these two gas pipelines. The recommended solution will be cheaper than if done by open cut. It has become apparent to staff, developers and local contractors that the gas pipeline industry has gradually been increasing construction safety standards within the limits of their easements. Assumptions made during design based on previous experiences are no longer valid. There have also been changes in pipeline ownership recently and every pipeline owner has their own safety and construction requirements. City staff is now going to greater lengths during the design of projects to accurately determine required construction methods and structure bid documents to assure the cost is captured, but there will still be incidents where field conditions result in modified methods.
The Director of Public Works will be in attendance at the meeting to answer Council’s questions regarding the proposed change order. A resolution is attached for Council’s consideration.
Funding Source
The funding source will be from the Street Bond Fund.
Prepared By
Ben Hartman, P.E., Project Engineer, Engineering Department
817-276-4295