Crews from the Hawkins Construction Company are hard at work to complete the Nebraska Department of Roads’ (NDOR) diverging diamond interchange (DDI) project in the city of Lincoln (Lancaster County), a $29 million project that began in June 2014 and will be completed in August 2016.
“The 2034 traffic numbers which warrant four lanes for the northwest 48th Street Diverging Diamond design assume a complete build-out of the surrounding land,” according to an NDOR Web page for the project. “An agreement was made between FHWA (Federal Highway Administration) and NDOR to construct the NW 48th Street Diverging Diamond in a ‘phased’ approach. NW 48th Street will be built with three lanes, but provide the necessary grading and right-of-way to allow for the fourth lane to be constructed when traffic numbers exceed the ‘phased’ design.”
The project brings together three items from the Build Nebraska Act Projects that are part of the original multiple six-lane expansion projects from Lincoln to Omaha, and cover work for the I-80: NW 48th Street Bridge, NW 56th Street to Hwy 77 South and NW 56th Street Bridge.
The project is being constructed in three phases, with each phase running for an entire construction season to complete.
“Phase I [constructed] two westbound I-80 lanes and a shoulder to the north of the existing lanes with minimal effects of existing traffic,” according to the Web page. “Phase II [is moving] westbound traffic to the new pavement and construct the interior lanes, while eastbound traffic remains on the existing lanes; [and] Phase III would hold all traffic on the new pavement during completion of the remaining eastbound pavement. NW 48th Street. [will] have a phased construction schedule concurrent with I-80. The NW 56th Street Bridge [will] be removed and closed early in the construction for two years.
“These projects are located on I-80 to the west of Lincoln, beginning west of NW 56th Street [Mile Marker 394.97], and tying into the previously completed six-lane expansion just west of NW 27th Street [Mile Marker 396.82] for a total of 1.85 miles.”
NDOR stresses the need for the work, noting that the projects are “the last part of the six-lane expansion of I-80 between NW 56th Street and Ruff Road that was covered by an environmental assessment document approved by FHWA on June 25, 2003. Initially constructed in 1961, improvements have been maintenance-related projects like pavement and/or shoulder replacement or overlay. The existing cross section of I-80 is a four-lane roadway consisting of two 24-ft. (7.3 m) roadways divided by a depressed turf median. Each direction has 6-ft. (1.8 m) inside shoulders of which 4 ft. are surfaced and 12-ft. (3.6 m) outside shoulders, of which 10 ft. (3 m) are surfaced.
“The I-80 traffic volumes, including heavy trucks, have continued to increase since this facility was opened,” according to the Web site. “Within this project location, heavy traffic volumes were 21.4 percent of the total traffic in 2009. A study has indicated that upgrading I-80 to six lanes, building three lanes in each direction would facilitate the estimated future traffic volumes. Reconstructing I-80 to six lanes [will] additionally require the reconstruction of the NW 48th Street Interchange to have the on/off ramps accommodate the interstate widening, as well as new I-80 bridges over NW 48th Street. A study called an Interchange Justification Report was completed in March 2012 and a Diverging Diamond Interchange has been chosen as the interchange concept to meet the future needs at NW 48th Street”
The I-80, traffic is expected to increase from 35,190 vehicles per-day in 2009 to 92,940 in 2034, with truck traffic remaining constant at 21 percent and for NW 48th Street, traffic should increase from 12,410 vehicles per-day to 58,535 in 2034, with the percentage of trucks going from 3.3 percent to 3.5 percent.
The work is extensive and requires a lot of planning and coordination between Hawkins Construction and NDOR.
“The Diverging Diamond Project, as with all other state projects, has a signed contract with specifications listing dates of phases or material limitations,” said Brian Johnson, NDOR’s roadway design interstate unit head. “On the site is an NDOR project manager to inspect the construction of the project and answer questions or seeks the answers from the specific design section which made the particular plan in question
“During the design of the project,” he said, “the intent of the phasing plans is to provide suitable areas for construction, keeping in mind the flow of traffic, safety of the traffic and contractor, and access to and from the phased area during the construction. The contractor will determine the location of a concrete or asphalt plant after the completion of the plans, so the design has to ensure that at least one access is possible. The contractor has the option to revise the phasing plan if an improved method which saves money for the NDOR or reduces time can be done while continuing to follow the limitations of traffic as dictated in the project contract. At all times the contractor must follow material specifications concerning time of delivery for concrete or allowable temperature ranges for asphalt at point of placement.”
NDOR does not provide specific locations for offices and materials as every contractor has different methods for coordinating the project.
“What NDOR will do during the creation of the construction phasing plans is allow for some distance from the end of the constructed area to the edge of traffic,” said Johnson. “The purpose is to allow the potential for the contractor to stockpile materials or provide room for construction equipment. In this particular project, a stockpile area for concrete removed from the existing pavement was provided at a location within the vicinity due to the amount of material removed from this project and during the construction of other six-lane projects. The concrete will be crushed and used as a foundation base for this project and future projects of I-80 heading west from Lincoln.”
During the creation of the plans for the project, several contractors were asked by NDOR about the phasing plans to see if the construction was possible.
“Then during the construction,” said Johnson, “if the contractor can show that a change improves the project cost or time by provided documentation, some form of incentive can be provided. The incentive could come in either a monetary way, NDOR paying for additional materials or an extension of working days provided.”
The NDOR work is impacting municipal infrastructure and utilities and commercial utilities.
“Roadway Design has been meeting with the city of Lincoln for several years prior to the project commencing to discuss everything from utilities, construction phasing, timing, storm water collection and even sidewalk routes,” said Johnson. “The meetings additionally ensured this project would coordinate with current and future municipal projects within the area.”
In addition to reconstructing I-80 with three lanes in each direction and a 28-ft. (8.5 m) wide paved median and a raised concrete barrier for positive separation between traffic, the existing West “O” Street on and off ramps are being removed because the location does not meet minimum interchange spacing and will improve mainline I-80 operations in this area. NW 48th Street is being reconstructed to allow three lanes and shoulders in either direction from West "O" Street north to West Vine Street and to improve traffic through the interchange, according to the web page.
NW 48th Street is being built as a diverging diamond with the use of traffic lights - traffic is essentially braided to reduce the traffic timing needed to allow left turns to occur,” it adds. “The intersection of NW 48th & West "O" Street will have left-turn and right-turn bays added to accommodate future traffic needs. The 2034 traffic numbers, which warrant four lanes for the NW 48th Street Diverging Diamond design, assume a complete build-out of the surrounding land. NW 56th Street [is being] rebuilt to provide a new bridge over I-80 to span the six lanes.”
Part of the traffic management plan for the project is to ensure access to local businesses is maintained throughout the work.
“Throughout the construction of the project, I-80 will have two lanes of traffic open in both directions, except for certain aspects of work that can only occur between 9:00 p.m. to 6:00 a.m.,” according to the web page. “NW 48th Street will be limited to a single lane in both directions for extended periods of time. NW 56th Street shall also remain open to the local businesses, but the bridge over I-80 will be closed for approximately two years from start of project. West “O” Street will have two lanes of traffic open in both directions except for certain aspects of work that can only occur between 9:00 p.m. to 6:00 a.m. I-80 and NW 48th Street would be closed and detoured on several occasions at night for removal of the existing bridges and placement of girders.”
Johnson said that the traffic plan is based lessons learned from other large projects, studies, and public meetings.
“A public hearing was held June 12, 2012, and the project was presented to the public,” he said. “All questions were discussed and the public was in favor of the project and construction process. Several parts of the project require the contractor to do work at nights and reduce impacts to traffic. The contract also limited the amount of time for the contractor working on the West O Street portion of the project. When something comes up which needs to be changed, the contractor and NDOR meet to discuss the possible changes for the phasing to improve the situation for everyone.”
NDOR acquired new right-of-way in the northwest and northeast quadrants of the NW 48th Street Interchange, around the intersection of West “O” Street and NW 48th Street, as well as some ROW along NW 56th Street. So far, no relocations are anticipated.
Crews are dealing with environmental issues and the design includes “mitigating stormwater discharges according to the Municipal Separate Storm Sewer Systems permitting process” and “wetlands will be delineated along the project and impacts determined as part of the re-evaluation of the environmental document.”
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