Braun Intertec has been involved in the Hiawatha Light Rail Transit (LRT) project from the preliminary investigative phases through the design and construction phases of this project. Our first work was in 1990, and trains are running in 2004.

Challenges

As a key component of a major metro area public transportation system, implementation of LRT in the Twin Cities is a complex initiative. This 11.5-mile corridor runs from the Mall of American in Bloomington, passing beneath the runways at the International Airport and back up to the VA Medical Center, along Hiawatha Avenue and through downtown Minneapolis. There are 16 stations along the corridor to serve riders, one yard and shop to service the 22 rail cars and 14 substations to house the electrical units.

Solutions:

Specific services we provided are detailed below:

Preliminary Geotechnical Investigation
We began preliminary geotechnical investigations for the alignment, working with BRW. The preliminary geotechnical investigations included collecting available geotechnical information along the proposed alignment, and completing supplemental soil borings. We provided preliminary soil correction recommendations for the rail alignment and the stations.

Geotechnical Engineering
After the final alignment was established, we provided supplemental soil borings for alignment and geotechnical recommendations for design and construction, including:

• Embankment design for the track subgrade and subdrainage
• Drilled pier recommendations for bridges and caternary poles
• Spread footing foundation for the stations, maintenance building, retaining walls, pedestrian bridge and electrical substations
• Noise wall foundation
• Mechanically stabilized earth retaining wall and stability review of contractor design
• Electrical resistivity testing for substation grounding
• City street pavement design

Geotechnical Engineering in Construction
We were onsite during construction to observe and provide geotechnical recommendations on the condition of the soils and bedrock.

Materials Testing
During construction, we provided quality assurance testing of companion samples of soils and concrete. We also provided nondestructive testing of steel in some of the bridges.

Property Assessments
Since several of the buildings adjacent to the LRT alignment in downtown Minneapolis are very old, there was some concern over the effects that new construction would have on existing structures. We provided property assessments on several structures to determine the conditions of structural before starting construction.

Environmental Investigations
We performed Phase I Environmental Site Assessments (ESA) for the properties along the alignment. Using the site history and use information generated from the Phase I ESAs, we developed plans for Phase II ESAs. The Phase II ESA would evaluate the site(s) through a series of backhoe test pits to evaluate former building areas and underlying soil conditions. In conjunction with the Minnesota Pollution Control Agency (MPCA), we devised a remediation plan for removing the soils. We were on site to monitor excavation and removal of the contaminated soils.